davinci: da850-evm: enable driver model for NAND

Enable the driver-model on da850-evm. 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>
Tested-by: Adam Ford <aford173@gmail.com> #da850-evm
diff --git a/configs/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index 7065205..96602e5 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -49,6 +49,7 @@
 CONFIG_DA8XX_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_DM_MMC=y
+CONFIG_MTD=y
 CONFIG_NAND=y
 CONFIG_NAND_DAVINCI=y
 CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y