Bluetooth: L2CAP: Move fixed channels to its own section in ROM

This changes the declaration of fixed channels to be statically defined
with use of BT_L2CAP_CHANNEL_DEFINE since fixed channels are never
unregistered.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
diff --git a/scripts/sanitycheck b/scripts/sanitycheck
index 662172c..26c55ae 100755
--- a/scripts/sanitycheck
+++ b/scripts/sanitycheck
@@ -909,8 +909,8 @@
     # These get copied into RAM only on non-XIP
     ro_sections = ["text", "ctors", "init_array", "reset", "object_access",
                    "rodata", "devconfig", "net_l2", "vector", "sw_isr_table",
-                   "_bt_settings_area", "_bt_services_area", "vectors",
-                   "net_socket_register"]
+                   "_bt_settings_area", "_bt_channels_area","_bt_services_area",
+                   "vectors", "net_socket_register"]
 
     def __init__(self, filename, extra_sections):
         """Constructor