V4L/DVB (12964): tuner-core: add support for NXP TDA18271 without TDA829X demod

Add support for NXP TDA18271 as a standalone tuner, allowing the use of
analog demodulators other than the Philips/NXP TDA829x.

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