V4L/DVB (12294): b2c2: Use dvb-pll for Cablestar2

The dvb-pll code should do the same thing that
alps_tdee4_stv0297_tuner_set_params() was doing.  Except the dvb-pll code
will check for tuner presence when attaching, while the old code didn't.

This tuner appears to not be behind the stv0297's I2C gate but is instead
on a different I2C adapter provided by the flexcop chip.  The old code
would turn the I2C gate off each time the tuner was used.  I've changed it
to turn the gate off when the tuner is attached and then disable the gate
control function.  This should result in the gate staying off, which should
be even better.

[hverkuil@xs4all.nl: fix compile error]

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>