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>

drivers/mmc/mmc.c

@@ -1068,8 +1068,7 @@ static int mmc_startup(struct mmc *mmc)
 
 			/* Read out group size from ext_csd */
 			mmc->erase_grp_size =
-				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] *
+				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] * 1024;
-					MMC_MAX_BLOCK_LEN * 1024;
 			/*
 			 * if high capacity and partition setting completed
 			 * SEC_COUNT is valid even if it is smaller than 2 GiB

include/mmc.h

@@ -315,7 +315,7 @@ struct mmc {
 	uint tran_speed;
 	uint read_bl_len;
 	uint write_bl_len;
-	uint erase_grp_size;
+	uint erase_grp_size;	/* in 512-byte sectors */
 	u64 capacity;
 	u64 capacity_user;
 	u64 capacity_boot;