btrfs: sink unlock_extent parameter gfp_flags

All callers pass either GFP_NOFS or GFP_KERNEL now, so we can sink the
parameter to the function, though we lose some of the slightly better
semantics of GFP_KERNEL in some places, it's worth cleaning up the
callchains.

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

fs/btrfs/disk-io.c

@@ -381,7 +381,7 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
 		clear_extent_buffer_uptodate(eb);
 out:
 	unlock_extent_cached(io_tree, eb->start, eb->start + eb->len - 1,
-			     &cached_state, GFP_NOFS);
+			     &cached_state);
 	if (need_lock)
 		btrfs_tree_read_unlock_blocking(eb);
 	return ret;