dm clone: Make __hash_find static

drivers/md/dm-clone-target.c:594:34: warning:
 symbol '__hash_find' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-clone-target.c

@@ -591,7 +591,7 @@ static struct hash_table_bucket *get_hash_table_bucket(struct clone *clone,
  *
  * NOTE: Must be called with the bucket lock held
  */
-struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket,
+static struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket,
 						     unsigned long region_nr)
 {
 	struct dm_clone_region_hydration *hd;