mmc: fix erase_grp_size computation with high-capacity size definition

The erase_grp_size in struct mmc is to be a size in 512-byte sectors
but the code used to compute it for eMMC when EXT_CSD_ERASE_GROUP_DEF is
enabled computed it as bytes, leading to erase sizes and alignment
much larger than what is actually required by the mmc device.

Signed-off-by: Diego Santa Cruz <Diego.SantaCruz@spinetix.com>
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index f07505f..be21101 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1068,8 +1068,7 @@
 
 			/* Read out group size from ext_csd */
 			mmc->erase_grp_size =
-				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] *
-					MMC_MAX_BLOCK_LEN * 1024;
+				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] * 1024;
 			/*
 			 * if high capacity and partition setting completed
 			 * SEC_COUNT is valid even if it is smaller than 2 GiB