davinci: omapl138-lcdk: enable driver model for NAND

Enable the driver-model on da850-lcdk. We need to add a dummy nand node
to the device tree, as the real nand node is a sub-node of the aemif
device.

On linux the aemif driver populates all its child nodes, but we can't do
it in u-boot currently.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
diff --git a/configs/omapl138_lcdk_defconfig b/configs/omapl138_lcdk_defconfig
index 7752308..fa4ce69 100644
--- a/configs/omapl138_lcdk_defconfig
+++ b/configs/omapl138_lcdk_defconfig
@@ -39,6 +39,7 @@
 CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_DAVINCI=y
 CONFIG_DM_MMC=y
+CONFIG_MTD=y
 CONFIG_NAND=y
 CONFIG_NAND_DAVINCI=y
 CONFIG_SYS_NAND_BUSWIDTH_16BIT=y