Add support for eMMC that reports newer revision.

Some second source eMMC parts report version 6, but should remain
compatible.

Change-Id: I1106099626219788849337995ad2ba5ea56020a6
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 8a3c7cd..628dbbf 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -259,7 +259,7 @@
 	}
 
 	card->ext_csd.rev = ext_csd[EXT_CSD_REV];
-	if (card->ext_csd.rev > 5) {
+	if (card->ext_csd.rev > 6) {
 		printk(KERN_ERR "%s: unrecognised EXT_CSD revision %d\n",
 			mmc_hostname(card->host), card->ext_csd.rev);
 		err = -EINVAL;