ext4: Clean up calls to ext4_get_group_desc()

If the caller isn't planning on modifying the block group descriptors,
there's no need to pass in a pointer to a struct buffer_head.  Nuking
this saves a tiny amount of CPU time and stack space usage.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index eca6c05..91b98b5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1660,7 +1660,6 @@
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_group_desc *gdp = NULL;
-	struct buffer_head *bh;
 	ext4_group_t flex_group_count;
 	ext4_group_t flex_group;
 	int groups_per_flex = 0;
@@ -1693,7 +1692,7 @@
 	}
 
 	for (i = 0; i < sbi->s_groups_count; i++) {
-		gdp = ext4_get_group_desc(sb, i, &bh);
+		gdp = ext4_get_group_desc(sb, i, NULL);
 
 		flex_group = ext4_flex_group(sbi, i);
 		atomic_set(&sbi->s_flex_groups[flex_group].free_inodes,