Convert CONFIG_SYS_INIT_RAM_LOCK to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_INIT_RAM_LOCK

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/T4240RDB_SDCARD_defconfig b/configs/T4240RDB_SDCARD_defconfig
index 8540abd..637e5cc 100644
--- a/configs/T4240RDB_SDCARD_defconfig
+++ b/configs/T4240RDB_SDCARD_defconfig
@@ -11,6 +11,7 @@
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL=y
 CONFIG_MPC85xx=y
+CONFIG_SYS_INIT_RAM_LOCK=y
 CONFIG_TARGET_T4240RDB=y
 CONFIG_ENABLE_36BIT_PHYS=y
 CONFIG_SYS_BOOK3E_HV=y