Revert "[nrf noup] boards: nordic: nrf54lm20 adjust ROM_START_OFFSET"

This reverts commit b407648.

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

Author: nordicjm

boards/nordic/nrf54lm20dk/Kconfig.defconfig

@@ -7,7 +7,6 @@ config HW_STACK_PROTECTION
 	default ARCH_HAS_STACK_PROTECTION
 
 config ROM_START_OFFSET
-	default 0 if PARTITION_MANAGER_ENABLED
 	default 0x800 if BOOTLOADER_MCUBOOT
 
 endif # BOARD_NRF54LM20DK_NRF54LM20A_CPUAPP