mmc: dw_mmc: remove unused EVENT_XFER_ERROR

EVENT_XFER_ERROR isn't been used now, so it can be removed.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

include/linux/mmc/dw_mmc.h

@@ -36,7 +36,6 @@ enum {
 	EVENT_XFER_COMPLETE,
 	EVENT_DATA_COMPLETE,
 	EVENT_DATA_ERROR,
-	EVENT_XFER_ERROR
 };
 
 struct mmc_data;