V4L/DVB (12257): em28xx: make tuning work for Terratec Cinergy T XS USB (mt352 variant)

The Terratec Cinergy T XS USB can have either a zl10353 or an mt352.  Add
support for the MT352 variant.

Thanks to Jelle de Jong for providing a unit to test/debug with.

Cc: Jelle de Jong <jelledejong@powercraft.nl>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>