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_defconfig b/configs/T4240RDB_defconfig
index 689b644..1d6280d 100644
--- a/configs/T4240RDB_defconfig
+++ b/configs/T4240RDB_defconfig
@@ -5,6 +5,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="t4240rdb"
 CONFIG_ENV_ADDR=0xEFF20000
 CONFIG_MPC85xx=y
+CONFIG_SYS_INIT_RAM_LOCK=y
 CONFIG_TARGET_T4240RDB=y
 CONFIG_MPC85XX_HAVE_RESET_VECTOR=y
 CONFIG_ENABLE_36BIT_PHYS=y