btrfs: remove unused typedefs get_extent_t and btrfs_work_func_t

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/async-thread.h

@@ -13,7 +13,6 @@ struct btrfs_fs_info;
 struct btrfs_workqueue;
 struct btrfs_work;
 typedef void (*btrfs_func_t)(struct btrfs_work *arg);
-typedef void (*btrfs_work_func_t)(struct work_struct *arg);
 
 struct btrfs_work {
 	btrfs_func_t func;

fs/btrfs/extent_io.h

@@ -142,10 +142,6 @@ static inline void extent_changeset_free(struct extent_changeset *changeset)
 
 struct extent_map_tree;
 
-typedef struct extent_map *(get_extent_t)(struct btrfs_inode *inode,
-					  struct page *page, size_t pg_offset,
-					  u64 start, u64 len);
-
 int try_release_extent_mapping(struct page *page, gfp_t mask);
 int try_release_extent_buffer(struct page *page);