V4L/DVB (12578): tda18271: allow drivers to request RF tracking filter calibration...

On certain master / slave dual tuner configurations, tuning performance
improves when the RF tracking filter calibration is performed sequentially.

This patch allows for the bridge driver to specify this behavior in the
configuration structure at attach-time.

The "cal" module option will continue to override this attach-time
configuration: set cal=0 to prevent RF tracking filter calibration
on startup, and set cal=1 to force it.

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