[media] media-entity: include linux/bug.h for WARN_ON

WARN_ON is used by this header file, but none of its direct includes
include asm/bug.h by way of linux/bug.h yet.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

include/media/media-entity.h

@@ -24,6 +24,7 @@
 #define _MEDIA_ENTITY_H
 
 #include <linux/bitmap.h>
+#include <linux/bug.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/media.h>