V4L/DVB (7028): tda18271: test RF_CAL_OK to see if we need additional RF calibration

Test RF_CAL_OK to see if we need to perform the RF tracking filter
calibration after returning from standby.

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