omapl138_lcdk: enable SPL MMC support

Enable SPL MMC support in order to allow to build a single u-boot image
that is able to boot from MMC and NAND devices.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/omapl138_lcdk_defconfig b/configs/omapl138_lcdk_defconfig
index d030ffa..77ede8a 100644
--- a/configs/omapl138_lcdk_defconfig
+++ b/configs/omapl138_lcdk_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_OMAPL138_LCDK=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y
 CONFIG_SPL_LIBGENERIC_SUPPORT=y
+CONFIG_SPL_MMC_SUPPORT=y
 CONFIG_SPL_NAND_SUPPORT=y
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_BOOTDELAY=3