btrfs: remove unnecessarily shadowed variables

In btrfs_orphan_cleanup, there's another instance of fs_info, but it's
the same as the one we already have.

In btrfs_backref_finish_upper_links, rb_node is same type and used
as temporary cursor to the tree.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/backref.c

@@ -2997,7 +2997,6 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 	while (!list_empty(&pending_edge)) {
 		struct btrfs_backref_node *upper;
 		struct btrfs_backref_node *lower;
-		struct rb_node *rb_node;
 
 		edge = list_first_entry(&pending_edge,
 				struct btrfs_backref_edge, list[UPPER]);

fs/btrfs/inode.c

@@ -3055,7 +3055,6 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
 
 		if (ret == -ENOENT && root == fs_info->tree_root) {
 			struct btrfs_root *dead_root;
-			struct btrfs_fs_info *fs_info = root->fs_info;
 			int is_dead_root = 0;
 
 			/*