dma-debug: track bucket lock state for static checkers

get_hash_bucket() and put_hash_bucket() acquire and release the same
spinlock, but this confuses static checkers such as sparse

  lib/dma-debug.c:254:27: warning: context imbalance in 'get_hash_bucket' - wrong count at exit
  lib/dma-debug.c:268:13: warning: context imbalance in 'put_hash_bucket' - unexpected unlock

Add the appropriate acquire and release statements so that checkers can
properly track the lock state.

Link: http://lkml.kernel.org/r/20160701191552.24295-1-sboyd@codeaurora.org
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/dma-debug.c

@@ -253,6 +253,7 @@ static int hash_fn(struct dma_debug_entry *entry)
  */
 static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
 					   unsigned long *flags)
+	__acquires(&dma_entry_hash[idx].lock)
 {
 	int idx = hash_fn(entry);
 	unsigned long __flags;
@@ -267,6 +268,7 @@ static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
  */
 static void put_hash_bucket(struct hash_bucket *bucket,
 			    unsigned long *flags)
+	__releases(&bucket->lock)
 {
 	unsigned long __flags = *flags;