r DBG_[SG]_REGISTER ioctls

Adds the advanced debugging register read/write ioctl support to the bttv
driver.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Bě 3›-x