ext4: avoid ext4_error when mounting a fs with a single bg

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

Remove some completely unneeded code which which caused an ext4_error
to be generated when mounting a file system with only a single block
group.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
---
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7b3ba42..4aa2040 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1445,7 +1445,6 @@ static int ext4_fill_flex_info(struct super_block *sb)
 	ext4_group_t flex_group_count;
 	ext4_group_t flex_group;
 	int groups_per_flex = 0;
-	__u64 block_bitmap = 0;
 	int i;
 
 	if (!sbi->s_es->s_log_groups_per_flex) {
@@ -1468,9 +1467,6 @@ static int ext4_fill_flex_info(struct super_block *sb)
 		goto failed;
 	}
 
-	gdp = ext4_get_group_desc(sb, 1, &bh);
-	block_bitmap = ext4_block_bitmap(sb, gdp) - 1;
-
 	for (i = 0; i < sbi->s_groups_count; i++) {
 		gdp = ext4_get_group_desc(sb, i, &bh);