[media] cx23885: Add DTV support for Mygica X8502/X8507 boards

Those boards were missing the ISDB-T support.
Most of the work on this patch were done by Alfredo.
My work here were to port this patch from Kernel 3.2 to upstream,
fix the issue caused by the set_frontend bad hook, and add the
Kconfig bits.
Tested on a X8502 board rebranded as:
"Leadership - Placa PCI-e de Captura de Vídeo Híbrida" - product code 3800.

Thanks-to: Alfredo Delaiti <alfredodelaiti@netscape.net>
Tested-by: Alfredo Delaiti <alfredodelaiti@netscape.net>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>