ext4: fix wrong unit use in ext4_mb_clear_bb

Function ext4_issue_discard need count in cluster. Pass count_clusters
instead of count to fix the mismatch.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: stable@kernel.org
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20230603150327.3596033-11-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -6280,8 +6280,8 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode,
 		 * them with group lock_held
 		 */
 		if (test_opt(sb, DISCARD)) {
-			err = ext4_issue_discard(sb, block_group, bit, count,
-						 NULL);
+			err = ext4_issue_discard(sb, block_group, bit,
+						 count_clusters, NULL);
 			if (err && err != -EOPNOTSUPP)
 				ext4_msg(sb, KERN_WARNING, "discard request in"
 					 " group:%u block:%d count:%lu failed"