btrfs: drop __must_check annotations

Drop all __must_check annotations because they're used in random
functions and not consistently. All errors should be handled.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.h

@@ -142,7 +142,7 @@ int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
 int btrfs_pin_reserved_extent(struct btrfs_trans_handle *trans, u64 start, u64 len);
 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans);
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans, struct btrfs_ref *generic_ref);
-int __must_check btrfs_drop_snapshot(struct btrfs_root *root, int update_ref,
+int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref,
 				     int for_reloc);
 int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root,

fs/btrfs/relocation.c

@@ -631,7 +631,7 @@ static int clone_backref_node(struct btrfs_trans_handle *trans,
 /*
  * helper to add 'address of tree root -> reloc tree' mapping
  */
-static int __must_check __add_reloc_root(struct btrfs_root *root)
+static int __add_reloc_root(struct btrfs_root *root)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct rb_node *rb_node;

fs/btrfs/root-tree.h

@@ -20,10 +20,8 @@ int btrfs_del_root(struct btrfs_trans_handle *trans, const struct btrfs_key *key
 int btrfs_insert_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		      const struct btrfs_key *key,
 		      struct btrfs_root_item *item);
-int __must_check btrfs_update_root(struct btrfs_trans_handle *trans,
-				   struct btrfs_root *root,
-				   struct btrfs_key *key,
-				   struct btrfs_root_item *item);
+int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		      struct btrfs_key *key, struct btrfs_root_item *item);
 int btrfs_find_root(struct btrfs_root *root, const struct btrfs_key *search_key,
 		    struct btrfs_path *path, struct btrfs_root_item *root_item,
 		    struct btrfs_key *root_key);