[media] media: use media_gobj inside pads

PADs also need unique object IDs that won't conflict with
the entity object IDs.

The pad objects are currently created via media_entity_init()
and, once created, never change.

While this will likely change in the future in order to
support dynamic changes, for now we'll keep PADs as arrays
and initialize the media_gobj embedded structs when
registering the entity.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
diff --git a/include/media/media-device.h b/include/media/media-device.h
index f6deef6..9493721 100644
--- a/include/media/media-device.h
+++ b/include/media/media-device.h
@@ -42,6 +42,7 @@
  * @hw_revision: Hardware device revision
  * @driver_version: Device driver version
  * @entity_id:	Unique ID used on the last entity registered
+ * @pad_id:	Unique ID used on the last pad registered
  * @entities:	List of registered entities
  * @lock:	Entities list lock
  * @graph_mutex: Entities graph operation lock
@@ -69,6 +70,7 @@
 	u32 driver_version;
 
 	u32 entity_id;
+	u32 pad_id;
 
 	struct list_head entities;