Convert CONFIG_LAST_STAGE_INIT to Kconfig

This converts the following to Kconfig:
   CONFIG_LAST_STAGE_INIT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/octeontx2_96xx_defconfig b/configs/octeontx2_96xx_defconfig
index 011bc79..ec03d95 100644
--- a/configs/octeontx2_96xx_defconfig
+++ b/configs/octeontx2_96xx_defconfig
@@ -24,6 +24,7 @@
 CONFIG_BOOTARGS="console=ttyAMA0,115200n8 earlycon=pl011,0x87e028000000 maxcpus=24 rootwait rw root=/dev/mmcblk0p2 coherent_pool=16M"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_BOARD_EARLY_INIT_R=y
+CONFIG_LAST_STAGE_INIT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Marvell> "
 # CONFIG_CMD_BOOTEFI_HELLO_COMPILE is not set