dm: mmc: socfpga: fix MMC_OPS support

Now that CONFIG_BLK and CONFIG_MMC_OPS are enabled by default with
CONFIG_DM_MMC, the DWMMC driver on the socfpga platform fails at
runtime.

This adds the missing fields in the driver declaration.

Signed-off-by: Sylvain Lesne <lesne@alse-fr.com>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>