V4L/DVB (7262): Add support for xc3028-based boards

V4L/DVB (7262): Add support for xc3028-based boards

This patch adds support for the following saa7134 xc3028 based boards:
132 -> AVerMedia Cardbus TV/Radio (E506R)       [1461:f436]
133 -> AVerMedia Hybrid TV/Radio (A16D)         [1461:f936]
134 -> Avermedia M115                           [1461:a836]
135 -> Compro VideoMate T750                    [185b:c900]

This is based on a original patch thanks to Markus Rechberger that added xc3028
gpio init code for the above boards.

This patch moves saa7134_tuner_callback to saa7134-cards, originally used only
by tda8290 DVB-S boards. The callback was made more generic to support other
tuners.

Currently, it supports both tda8290 and xc2028/xc3028 tuners. Added also the
basis for xc5000 tuner callback.

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