V4L/DVB (4814): Remote support for Avermedia 777

I didn't test it personally since I don't have this card, but A16AR uses the
same interface and that one certainly does work perfectly (see the next patch).
This patch was originally sent in
	http://marc.theaimsgroup.com/?l=linux-video&m=114743413825375&w=2
	https://www.redhat.com/mailman/private/video4linux-list/2006-May/msg00103.html
but never got applied. This version has some trivial modifications and drops
the weird gpio hack (it's not clear what practical purpose does it serve).

Signed-off-by: Jose Alberto Reguero <jareguero@telefonica.net>
Signed-off-by: Petr Baudis <pasky@ucw.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>