[media] media: Add pad flag MEDIA_PAD_FL_MUST_CONNECT

Pads that set this flag must be connected by an active link for the entity
to stream.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
index ed49574..d847c76 100644
--- a/include/uapi/linux/media.h
+++ b/include/uapi/linux/media.h
@@ -98,6 +98,7 @@
 
 #define MEDIA_PAD_FL_SINK		(1 << 0)
 #define MEDIA_PAD_FL_SOURCE		(1 << 1)
+#define MEDIA_PAD_FL_MUST_CONNECT	(1 << 2)
 
 struct media_pad_desc {
 	__u32 entity;		/* entity ID */