md: remove sparse warnings about lock context.

There was a real error here on a failure path where we
incorrectly call rcu_read_unlock.


Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 3319c2f..6986b00 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -108,6 +108,8 @@
  * allocated while we're using it
  */
 static int bitmap_checkpage(struct bitmap *bitmap, unsigned long page, int create)
+__releases(bitmap->lock)
+__acquires(bitmap->lock)
 {
 	unsigned char *mappage;
 
@@ -325,7 +327,6 @@
 	return 0;
 
  bad_alignment:
-	rcu_read_unlock();
 	return -EINVAL;
 }
 
@@ -1207,6 +1208,8 @@
 static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
 					    sector_t offset, int *blocks,
 					    int create)
+__releases(bitmap->lock)
+__acquires(bitmap->lock)
 {
 	/* If 'create', we might release the lock and reclaim it.
 	 * The lock must have been taken with interrupts enabled.