media: mediactl/*.rst: document argp

The documentation of the Media Controller API ioctls is missing a description
of the argp ioctl argument. Add this.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/media/uapi/mediactl/media-ioc-device-info.rst

@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_device_info`.
 
 
 Description

Documentation/media/uapi/mediactl/media-ioc-enum-entities.rst

@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_entity_desc`.
 
 
 Description

Documentation/media/uapi/mediactl/media-ioc-enum-links.rst

@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_links_enum`.
 
 
 Description

Documentation/media/uapi/mediactl/media-ioc-g-topology.rst

@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_v2_topology`.
 
 
 Description

Documentation/media/uapi/mediactl/media-ioc-setup-link.rst

@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_link_desc`.
 
 
 Description