scripts: ci: check_compliance: Add Kconfig to allow list

Adds a Kconfig used in MCUboot to the allow list

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

scripts/ci/check_compliance.py

@@ -1015,6 +1015,7 @@ def check_no_undef_outside_kconfig(self, kconf):
         "BOOT_ENCRYPTION_KEY_FILE", # Used in sysbuild
         "BOOT_ENCRYPT_IMAGE", # Used in sysbuild
         "BOOT_FIRMWARE_LOADER", # Used in sysbuild for MCUboot configuration
+        "BOOT_FIRMWARE_LOADER_BOOT_MODE", # Used in sysbuild for MCUboot configuration
         "BOOT_MAX_IMG_SECTORS_AUTO", # Used in sysbuild
         "BOOT_RAM_LOAD", # Used in sysbuild for MCUboot configuration
         "BOOT_SERIAL_BOOT_MODE",     # Used in (sysbuild-based) test/