V4L/DVB (6430): Convert tuner-xc2028 driver to the newer hybrid approach

This changeset converts tuner-xc2028 to the newer hybrid approach. It also
prevents creating twice the xc3028 private struct by both DVB and V4L parts.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>