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>
diff --git a/configs/am335x_sl50_defconfig b/configs/am335x_sl50_defconfig
index 238164a..0aeaad5 100644
--- a/configs/am335x_sl50_defconfig
+++ b/configs/am335x_sl50_defconfig
@@ -52,6 +52,7 @@
 CONFIG_MII=y
 CONFIG_DRIVER_TI_CPSW=y
 CONFIG_SPI=y
+CONFIG_DM_SPI=y
 CONFIG_OMAP3_SPI=y
 CONFIG_FAT_WRITE=y
 CONFIG_LZO=y