V4L/DVB (5162): Change VIDIOC_DBG_[SG]_REGISTER ioctls' reg address to 64 bits

Maybe someday there will be a device with a register address space >
32-bits, or maybe an i2c device which uses a protocol > 4 bytes long to
address its registers.

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