[media] v4l2-ctrl: Add helper function for the controls range update

This patch adds a helper function that allows to modify range,
i.e. minimum, maximum, step and default value of a v4l2 control,
after the control has been created and initialized. This is helpful
in situations when range of a control depends on user configurable
parameters, e.g. camera sensor absolute exposure time depending on
an output image resolution and frame rate.
v4l2_ctrl_modify_range() function allows to modify range of an
INTEGER, BOOL, MENU, INTEGER_MENU and BITMASK type controls.
Based on a patch from Hans Verkuil http://patchwork.linuxtv.org/patch/8654.

Signed-off-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml
index ebd2bfd..104a1a2 100644
--- a/Documentation/DocBook/media/v4l/compat.xml
+++ b/Documentation/DocBook/media/v4l/compat.xml
@@ -2486,6 +2486,10 @@
 	  <structname>v4l2_buffer</structname>. See <xref
 	  linkend="buffer-flags" />.</para>
         </listitem>
+        <listitem>
+	  <para>Added <constant>V4L2_EVENT_CTRL_CH_RANGE</constant> control event
+	  changes flag. See <xref linkend="changes-flags"/>.</para>
+        </listitem>
       </orderedlist>
     </section>