boards: remove `HCI_SPI` defaults

The `HCI_SPI` symbol is now automatically selected from devicetree,
removing the need for board specific defaults.

Signed-off-by: Jordan Yates <jordan@embeint.com>
diff --git a/boards/96boards/carbon/Kconfig.defconfig b/boards/96boards/carbon/Kconfig.defconfig
index 2cf1bbd..3fe660f 100644
--- a/boards/96boards/carbon/Kconfig.defconfig
+++ b/boards/96boards/carbon/Kconfig.defconfig
@@ -9,16 +9,6 @@
 	default y
 	depends on SPI
 
-if BT
-
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
-endif # BT
-
 endif # BOARD_96B_CARBON_STM32F401XE
 
 if BOARD_96B_CARBON_NRF51822
diff --git a/boards/shields/x_nucleo_bnrg2a1/Kconfig.defconfig b/boards/shields/x_nucleo_bnrg2a1/Kconfig.defconfig
index 94ace9e..0c42f5d 100644
--- a/boards/shields/x_nucleo_bnrg2a1/Kconfig.defconfig
+++ b/boards/shields/x_nucleo_bnrg2a1/Kconfig.defconfig
@@ -5,12 +5,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 
diff --git a/boards/shields/x_nucleo_idb05a1/Kconfig.defconfig b/boards/shields/x_nucleo_idb05a1/Kconfig.defconfig
index 276ee66..4e346ea 100644
--- a/boards/shields/x_nucleo_idb05a1/Kconfig.defconfig
+++ b/boards/shields/x_nucleo_idb05a1/Kconfig.defconfig
@@ -5,12 +5,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 # Disable Flow control
diff --git a/boards/shields/x_nucleo_wb05kn1/Kconfig.defconfig b/boards/shields/x_nucleo_wb05kn1/Kconfig.defconfig
index 9ca3447..dae0d61 100644
--- a/boards/shields/x_nucleo_wb05kn1/Kconfig.defconfig
+++ b/boards/shields/x_nucleo_wb05kn1/Kconfig.defconfig
@@ -5,22 +5,10 @@
 
 if BT
 
-config SPI
-	default y
-	depends on SHIELD_X_NUCLEO_WB05KN1_SPI
-
 config SPI_STM32_INTERRUPT
 	default y
 	depends on SPI
 
-config BT_SPI
-	default y
-	depends on DT_HAS_ST_HCI_SPI_V2_ENABLED
-
-config BT_H4
-	default y
-	depends on DT_HAS_ZEPHYR_BT_HCI_UART_ENABLED
-
 config BT_BLUENRG_ACI
 	default y
 
diff --git a/boards/st/b_l4s5i_iot01a/Kconfig.defconfig b/boards/st/b_l4s5i_iot01a/Kconfig.defconfig
index 317d096..8e2d927 100644
--- a/boards/st/b_l4s5i_iot01a/Kconfig.defconfig
+++ b/boards/st/b_l4s5i_iot01a/Kconfig.defconfig
@@ -24,12 +24,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 # Disable Flow control
diff --git a/boards/st/disco_l475_iot1/Kconfig.defconfig b/boards/st/disco_l475_iot1/Kconfig.defconfig
index 808425e..68ede55 100644
--- a/boards/st/disco_l475_iot1/Kconfig.defconfig
+++ b/boards/st/disco_l475_iot1/Kconfig.defconfig
@@ -24,12 +24,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 # Disable Flow control
diff --git a/boards/st/sensortile_box/Kconfig.defconfig b/boards/st/sensortile_box/Kconfig.defconfig
index faa5dc0..24d16b1 100644
--- a/boards/st/sensortile_box/Kconfig.defconfig
+++ b/boards/st/sensortile_box/Kconfig.defconfig
@@ -7,12 +7,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 # Disable Flow control
diff --git a/boards/st/sensortile_box_pro/Kconfig.defconfig b/boards/st/sensortile_box_pro/Kconfig.defconfig
index fb701bd..fffa4f4 100644
--- a/boards/st/sensortile_box_pro/Kconfig.defconfig
+++ b/boards/st/sensortile_box_pro/Kconfig.defconfig
@@ -7,12 +7,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 
diff --git a/boards/st/steval_stwinbx1/Kconfig.defconfig b/boards/st/steval_stwinbx1/Kconfig.defconfig
index 657170d..35256e0 100644
--- a/boards/st/steval_stwinbx1/Kconfig.defconfig
+++ b/boards/st/steval_stwinbx1/Kconfig.defconfig
@@ -7,12 +7,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 
diff --git a/boards/st/stm32l562e_dk/Kconfig.defconfig b/boards/st/stm32l562e_dk/Kconfig.defconfig
index b0dc8f3..118968f 100644
--- a/boards/st/stm32l562e_dk/Kconfig.defconfig
+++ b/boards/st/stm32l562e_dk/Kconfig.defconfig
@@ -7,12 +7,6 @@
 
 if BT
 
-config SPI
-	default y
-
-config BT_SPI
-	default y
-
 config BT_BLUENRG_ACI
 	default y
 
diff --git a/doc/releases/migration-guide-4.0.rst b/doc/releases/migration-guide-4.0.rst
index e68dfb4..b3ec144 100644
--- a/doc/releases/migration-guide-4.0.rst
+++ b/doc/releases/migration-guide-4.0.rst
@@ -330,6 +330,8 @@
 
 * The ``bt-hci-bus`` and ``bt-hci-quirks`` devicetree properties for HCI bindings have been changed
   to use lower-case strings without the ``BT_HCI_QUIRK_`` and ``BT_HCI_BUS_`` prefixes.
+* The Kconfig option :kconfig:option:`BT_SPI` is now automatically selected based on devicetree
+  compatibles and can be removed from board ``.defconfig`` files.
 
 Bluetooth Mesh
 ==============