[media] media: Fix a compiler warning in media_entity_pipeline_start()

Patch "[media] media: Print information on failed link validation" cause a
harmless compiler warning in printing a debug message. Fix this.

The type casting is done do ensure the type really is suitable for printing
as %u, as find_first_zero_bit() does return int on some architectures and
unsigned long on others.
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/media-entity.c

@@ -297,7 +297,8 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity,
 			dev_dbg(entity->parent->dev,
 				"\"%s\":%u must be connected by an enabled link\n",
 				entity->name,
-				find_first_zero_bit(active, entity->num_pads));
+				(unsigned)find_first_zero_bit(
+					active, entity->num_pads));
 			goto error;
 		}
 	}