[nrf noup] soc: nordic: nrf54l: Add ROM start offset PM override

Adds an override to force this Kconfig to 0 when partition manager
is enabled

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
(cherry picked from commit cf7c4d3)

Author: nordicjm

soc/nordic/nrf54l/Kconfig.defconfig

@@ -33,6 +33,7 @@ choice NULL_POINTER_EXCEPTION_DETECTION
 endchoice
 
 config ROM_START_OFFSET
+	default 0 if PARTITION_MANAGER_ENABLED
 	default 0x800 if BOOTLOADER_MCUBOOT && !BUILD_WITH_TFM
 
 endif # ARM