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/board/freescale/common/Kconfig b/board/freescale/common/Kconfig
index 8a9a9be..a5e302f 100644
--- a/board/freescale/common/Kconfig
+++ b/board/freescale/common/Kconfig
@@ -2,5 +2,6 @@
 	depends on !FIT_SIGNATURE && SECURE_BOOT
 	imply CMD_BLOB
 	select FSL_CAAM
+	select SPL_BOARD_INIT if (ARM && SPL)
 	bool
 	default y