boards: frdm_rw612: align Kconfig.defconfig with upsteam

Zephyr upstream removed the FLASH_LOAD_SIZE setting from the
board's defconfig.

Signed-off-by: David Leach <[email protected]>

Author: dleach02

boards/nxp/frdm_rw612/Kconfig.defconfig

@@ -5,9 +5,6 @@
 
 if BOARD_FRDM_RW612
 
-config FLASH_LOAD_SIZE
-	default 0x400000 if !BOOTLOADER_MCUBOOT && !(NXP_MONOLITHIC_WIFI || NXP_MONOLITHIC_BT)
-
 config NET_L2_ETHERNET
 	default y if DT_HAS_NXP_ENET_MAC_ENABLED && NETWORKING