_[SG]_REGISTER calls

Add support for these ioctls to the video_ioctl2 system and the cx88
driver.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
%c˜M™#x