btrfs: Remove useless variable in write_ctree_super()

The function write_ctree_super() in disk-io.c uses variable ret to return
the result of function write_all_supers(). Since, this variable serves
no purpose, hence the patch removes it and returns the call of the
called function.
Reviewed-by: Zach Brown <zab@redhat.com>
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/disk-io.c

@@ -3440,10 +3440,7 @@ static int write_all_supers(struct btrfs_root *root, int max_mirrors)
 int write_ctree_super(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *root, int max_mirrors)
 {
-	int ret;
-
-	ret = write_all_supers(root, max_mirrors);
-	return ret;
+	return write_all_supers(root, max_mirrors);
 }
 
 /* Drop a fs root from the radix tree and free it. */