dm: rockchip: Enable CONFIG_BLK

Enable CONFIG_BLK to move to using driver model for block devices. This
affects MMC booting in SPL, as well as MMC access in U-Boot proper.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/arm/mach-rockchip/Kconfig

@@ -41,6 +41,9 @@ config DM_I2C
 config DM_GPIO
 	default y
 
+config BLK
+	default y
+
 source "arch/arm/mach-rockchip/rk3288/Kconfig"
 source "arch/arm/mach-rockchip/rk3036/Kconfig"
 endif