dm vdo dedupe: silence sparse warnings about locking context imbalances

Annotate both open_index() and close_index() with
__must_hold(&zones->lock) to silence these sparse warnings:
 warning: context imbalance in 'close_index' - unexpected unlock
 warning: context imbalance in 'open_index' - unexpected unlock
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Susan LeGendre-McGhee <slegendr@redhat.com>
Signed-off-by: Matthew Sakai <msakai@redhat.com>

drivers/md/dm-vdo/dedupe.c

@@ -2092,6 +2092,7 @@ static void finish_uds_queue(void *ptr __always_unused)
 }
 
 static void close_index(struct hash_zones *zones)
+	__must_hold(&zones->lock)
 {
 	int result;
 
@@ -2113,6 +2114,7 @@ static void close_index(struct hash_zones *zones)
 }
 
 static void open_index(struct hash_zones *zones)
+	__must_hold(&zones->lock)
 {
 	/* ASSERTION: We enter in IS_CLOSED state. */
 	int result;