Btrfs: fix uninit warning in backref.c

Added initialization with the declaration of ret. It isn't set later on the
switch-default branch (which should never be taken).
Signed-off-by: NJan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

fs/btrfs/backref.c

@@ -297,7 +297,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 	struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 	struct rb_node *n = &head->node.rb_node;
 	int sgn;
-	int ret;
+	int ret = 0;
 
 	if (extent_op && extent_op->update_key)
 		btrfs_disk_key_to_cpu(info_key, &extent_op->key);
@@ -392,7 +392,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 			     struct btrfs_key *info_key, int *info_level,
 			     struct list_head *prefs)
 {
-	int ret;
+	int ret = 0;
 	int slot;
 	struct extent_buffer *leaf;
 	struct btrfs_key key;