[media] v4l: Fix ARGB32 fourcc value in the documentation

The ARGB32 pixel format's fourcc value is defined to 'BA24' in the
videodev2.h header, but documented as 'AX24'. Fix the documentation.
Reported-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml

@@ -486,7 +486,7 @@ for a pixel lie next to each other in memory.</para>
 	  </row>
 	  <row id="V4L2-PIX-FMT-ARGB32">
 	    <entry><constant>V4L2_PIX_FMT_ARGB32</constant></entry>
-	    <entry>'AX24'</entry>
+	    <entry>'BA24'</entry>
 	    <entry></entry>
 	    <entry>a<subscript>7</subscript></entry>
 	    <entry>a<subscript>6</subscript></entry>