[media] cx231xx: properly implement URB control messages log

This allows usage of a tool at v4l-utils tree to parse URB messages
and display them to userspace. The tool is available at:

http://git.linuxtv.org/v4l-utils.git?a=blob;f=contrib/cx231xx/parse_cx231xx.pl;hb=HEAD



Acked-by: Sri Deevi <Srinivasa.Deevi@conexant.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>