V4L/DVB (11364): tuner: remove i2c legacy code.

All drivers that use the tuner module now use v4l2_subdev, so we can remove the
legacy code from this module.

Note that TUNER_SET_CONFIG is still called by tuner-simple.c, so we have
to handle it via a .command callback. There must be a better way to do this,
but for now this will work.

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