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/MPC8548CDS_legacy_defconfig b/configs/MPC8548CDS_legacy_defconfig
index ef92c7b..a5747c9 100644
--- a/configs/MPC8548CDS_legacy_defconfig
+++ b/configs/MPC8548CDS_legacy_defconfig
@@ -7,6 +7,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="mpc8548cds"
 CONFIG_ENV_ADDR=0xFFF60000
 CONFIG_MPC85xx=y
+CONFIG_SYS_INIT_RAM_LOCK=y
 # CONFIG_CMD_ERRATA is not set
 CONFIG_TARGET_MPC8548CDS=y
 CONFIG_MPC85XX_HAVE_RESET_VECTOR=y