V4L/DVB (7136): tda18271: use hybrid_tuner_request_state to manage tuner instances

Convert tda18271 to use the new hybrid_tuner_request_state and
hybrid_tuner_release_state macros to manage state sharing between
hybrid tuner instances.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>