btrfs: open code rbtree search in insert_state

The rbtree search is a known pattern and can be open coded, allowing to
remove the tree_insert and further cleanups.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2020-06-25 17:14:17 +02:00
commit c7e118cf98