V4L/DVB (7121): Renames videobuf lock to vb_lock

This helps to identify where vb_lock is being used, and find missusages of the
locks.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/video/videobuf-vmalloc.c b/drivers/media/video/videobuf-vmalloc.c
index 9b38983..03b3b41 100644
--- a/drivers/media/video/videobuf-vmalloc.c
+++ b/drivers/media/video/videobuf-vmalloc.c
@@ -70,7 +70,7 @@
 	map->count--;
 	if (0 == map->count) {
 		dprintk(1,"munmap %p q=%p\n",map,q);
-		mutex_lock(&q->lock);
+		mutex_lock(&q->vb_lock);
 		for (i = 0; i < VIDEO_MAX_FRAME; i++) {
 			if (NULL == q->bufs[i])
 				continue;
@@ -83,7 +83,7 @@
 			q->bufs[i]->map   = NULL;
 			q->bufs[i]->baddr = 0;
 		}
-		mutex_unlock(&q->lock);
+		mutex_unlock(&q->vb_lock);
 		kfree(map);
 	}
 	return;