[media] c8sectpfe: use a new Kconfig menu for DVB platform drivers

While this is the first DVB platform drivers, let's keep the
Kconfig options well organized, adding it on its own DVB menu.

Of course, it should depend on MEDIA_DIGITAL_TV_SUPPORT, as
this enables all DVB-related menus.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>