btrfs: open code rbtree search in split_state

Preparatory work to remove tree_insert from extent_io.c, the rbtree
search loop is a known and simple so it can be open coded.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2020-06-25 16:49:48 +02:00
commit 12c9cdda62