Revert "[nrf noup] boards: nrf54l15pdk: ROM_START_OFFSET"

This reverts commit 9a0b81b.

Signed-off-by: Grzegorz Swiderski <[email protected]>

Author: 57300

boards/nordic/nrf54l15pdk/Kconfig.defconfig

@@ -7,7 +7,6 @@ config BT_CTLR
 	default BT
 
 config ROM_START_OFFSET
-	default 0 if PARTITION_MANAGER_ENABLED
 	default 0x800 if BOOTLOADER_MCUBOOT
 
 endif # BOARD_NRF54L15PDK_NRF54L15_CPUAPP