[media] v4l: Document EACCES in VIDIOC_[GS]_CTRL and VIDIOC_{G, S, TRY}_EXT_CTRLS

VIDIOC_S_CTRL and VIDIOC_S_EXT_CTRLS return EACCES when setting a read-only
control VIDIOC_TRY_EXT_CTRLS when trying a read-only control and
VIDIOC_G_CTRL and VIDIOC_G_EXT_CTRLS when getting a write-only control.
Document this.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/vidioc-g-ctrl.xml

@@ -117,6 +117,13 @@ because another applications took over control of the device function
 this control belongs to.</para>
 	</listitem>
       </varlistentry>
+      <varlistentry>
+	<term><errorcode>EACCES</errorcode></term>
+	<listitem>
+	  <para>Attempt to set a read-only control or to get a
+	  write-only control.</para>
+	</listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>

Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml

@@ -294,6 +294,13 @@ The field <structfield>size</structfield> is set to a value that is enough
 to store the payload and this error code is returned.</para>
 	</listitem>
       </varlistentry>
+      <varlistentry>
+	<term><errorcode>EACCES</errorcode></term>
+	<listitem>
+	  <para>Attempt to try or set a read-only control or to get a
+	  write-only control.</para>
+	</listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>