[media] bttv: Add support for PCI-8604PW

This patch adds support for the PCI-8604PW card equipped with four 878A.
It is unknown who the manufacturer of this card is and no drivers were
available during development of the patch. According to images found
online, the card is originally sold with Linux DVR software.

A CPLD on the card prevents the 878A from requesting access to the
bus until an initialization sequence has been issued via GPIOs. The
implemented sequence uses the minimum number of GPIOs needed to
successfully unlock bus access. As there are many more GPIOs connected
to the CPLD, it is very likely that some of the others have an influence
on the bus arbitration scheduling. This should be investigated further
in case of performance issues.

The tested card contains an EEPROM on one of the 878A, but it is
completely empty (i.e. contains only 0xff), so it is not possible
to detect the card.

Signed-off-by: Daniel Glöckner <daniel-gl@gmx.net>
Tested-by: Robert Longbottom <rongblor@googlemail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>