Convert CONFIG_SPL_BOARD_INIT to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_BOARD_INIT

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
[trini: Update the Kconfig logic]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mccmon6_nor_defconfig b/configs/mccmon6_nor_defconfig
index 7744fcb..acc43ad 100644
--- a/configs/mccmon6_nor_defconfig
+++ b/configs/mccmon6_nor_defconfig
@@ -7,6 +7,7 @@
 # CONFIG_CMD_BMODE is not set
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/liebherr/mccmon6/mon6_imximage_nor.cfg,MX6QDL"
 CONFIG_SPL=y
+CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_NOR_SUPPORT=y
 CONFIG_HUSH_PARSER=y