am335x: sl50: Enable DM_SPI
Enable DM_SPI for am355x sl50 board.
Build is fine, but not tested.
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>