btrfs: Remove extent_io_ops::clear_bit_hook callback

This is the counterpart to ex-set_bit_hook (now btrfs_set_delalloc_extent),
similar to what was done before remove clear_bit_hook and rename the
function. No functional changes.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3152,6 +3152,8 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     u64 new_dirid);
 void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
 			       unsigned *bits);
+void btrfs_clear_delalloc_extent(struct inode *inode,
+				 struct extent_state *state, unsigned *bits);
 int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags);