Btrfs: sparse lock verification annotations for wait_on_state

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 87dba85..d79ccdb 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -577,6 +577,8 @@
 
 static int wait_on_state(struct extent_io_tree *tree,
 			 struct extent_state *state)
+		__releases(tree->lock)
+		__acquires(tree->lock)
 {
 	DEFINE_WAIT(wait);
 	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);