V4L/DVB (13164): DocBook/dvb: Starts documenting DVBS2API ioctls

DVBS2API introduced two new ioctls that allows changing/getting details about newer
video standards like DVB-S2 and ISDB-T. There are lots of thing to do in this chapter,
but, for now, just add a session there, in order to allow make to not complain about
undefined symbol.

With this patch, all ioctls at the frontend.h API were somehow documented.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/dvb/dvbproperty.xml

+<section id="FE_GET_PROPERTY">
+<title>FE_GET_PROPERTY/FE_SET_PROPERTY</title>
+
 <section id="isdbt">
 	<title>ISDB-T frontend</title>
 	<para>This section describes shortly what are the possible parameters in the Linux
@@ -312,3 +315,4 @@
 		</section>
 	</section>
 </section>
+</section>