V4L/DVB (13215): tda18271: add support for the set_config method

Add the set_config method to allow drivers to configure the
tda18271 driver options after attach.

Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>