uboot-imx

configs: omapl138: Enable DM and DT

Enable Driver Model and Device-tree support for omapl138 board
in U-Boot. Also enable DM_SERIAL and DM_I2C.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>