V4L/DVB (7029): tda18271: provide a choice whether to perform rf cal on init or on first tune

If module option "cal" is set to 1, the ~22 sec rf tracking filter calibration
sequence will be invoked on startup.  Otherwise, the calibration will take
place during the first tune.

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