sam0: flash: Fix build issue reported by flash_shell sample

The DT_FLASH_DEV_NAME define used by the sample was set to a define
symbol that was never generated.  Change it to use
DT_INST_0_ATMEL_SAM0_NVMCTRL_LABEL on the sam0 family of SoCs that
had this issue.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
diff --git a/soc/arm/atmel_sam0/samd51/dts_fixup.h b/soc/arm/atmel_sam0/samd51/dts_fixup.h
index 9179b34..51a75e7 100644
--- a/soc/arm/atmel_sam0/samd51/dts_fixup.h
+++ b/soc/arm/atmel_sam0/samd51/dts_fixup.h
@@ -6,7 +6,7 @@
 
 /* SoC level DTS fixup file */
 
-#define DT_FLASH_DEV_NAME DT_ATMEL_SAM0_NVMCTRL_0_LABEL
+#define DT_FLASH_DEV_NAME DT_INST_0_ATMEL_SAM0_NVMCTRL_LABEL
 
 #define DT_NUM_IRQ_PRIO_BITS	DT_ARM_V7M_NVIC_E000E100_ARM_NUM_IRQ_PRIORITY_BITS
 
diff --git a/soc/arm/atmel_sam0/same51/dts_fixup.h b/soc/arm/atmel_sam0/same51/dts_fixup.h
index 9179b34..51a75e7 100644
--- a/soc/arm/atmel_sam0/same51/dts_fixup.h
+++ b/soc/arm/atmel_sam0/same51/dts_fixup.h
@@ -6,7 +6,7 @@
 
 /* SoC level DTS fixup file */
 
-#define DT_FLASH_DEV_NAME DT_ATMEL_SAM0_NVMCTRL_0_LABEL
+#define DT_FLASH_DEV_NAME DT_INST_0_ATMEL_SAM0_NVMCTRL_LABEL
 
 #define DT_NUM_IRQ_PRIO_BITS	DT_ARM_V7M_NVIC_E000E100_ARM_NUM_IRQ_PRIORITY_BITS
 
diff --git a/soc/arm/atmel_sam0/same53/dts_fixup.h b/soc/arm/atmel_sam0/same53/dts_fixup.h
index 9179b34..51a75e7 100644
--- a/soc/arm/atmel_sam0/same53/dts_fixup.h
+++ b/soc/arm/atmel_sam0/same53/dts_fixup.h
@@ -6,7 +6,7 @@
 
 /* SoC level DTS fixup file */
 
-#define DT_FLASH_DEV_NAME DT_ATMEL_SAM0_NVMCTRL_0_LABEL
+#define DT_FLASH_DEV_NAME DT_INST_0_ATMEL_SAM0_NVMCTRL_LABEL
 
 #define DT_NUM_IRQ_PRIO_BITS	DT_ARM_V7M_NVIC_E000E100_ARM_NUM_IRQ_PRIORITY_BITS
 
diff --git a/soc/arm/atmel_sam0/same54/dts_fixup.h b/soc/arm/atmel_sam0/same54/dts_fixup.h
index 9179b34..51a75e7 100644
--- a/soc/arm/atmel_sam0/same54/dts_fixup.h
+++ b/soc/arm/atmel_sam0/same54/dts_fixup.h
@@ -6,7 +6,7 @@
 
 /* SoC level DTS fixup file */
 
-#define DT_FLASH_DEV_NAME DT_ATMEL_SAM0_NVMCTRL_0_LABEL
+#define DT_FLASH_DEV_NAME DT_INST_0_ATMEL_SAM0_NVMCTRL_LABEL
 
 #define DT_NUM_IRQ_PRIO_BITS	DT_ARM_V7M_NVIC_E000E100_ARM_NUM_IRQ_PRIORITY_BITS