btrfs: extent-tree: Use btrfs_ref to refactor btrfs_inc_extent_ref()

Now we don't need to play the dirty game of reusing @owner for tree block
level.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
7 files changed