binder: fix sparse warnings on locking context

Add __acquire()/__release() annnotations to fix warnings
in sparse context checking

There is one case where the warning was due to a lack of
a "default:" case in a switch statement where a lock was
being released in each of the cases, so the default
case was added.

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 64fd96e..52eb11e 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -943,6 +943,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 				       struct list_lru_one *lru,
 				       spinlock_t *lock,
 				       void *cb_arg)
+	__must_hold(lock)
 {
 	struct mm_struct *mm = NULL;
 	struct binder_lru_page *page = container_of(item,