mmc: use right timing mode constant

Fix copy-n-paste error.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index e8f896c..2ba4627 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1145,7 +1145,7 @@
 
 			mmc_card_set_highspeed(card);
 
-			host->ios.timing = MMC_TIMING_SD_HS;
+			host->ios.timing = MMC_TIMING_MMC_HS;
 			mmc_set_ios(host);
 		}