V4L/DVB (4662): Pvrusb2: Implement VIDIOC_INT_[G|S]_REGISTER

Implement VIDIOC_INT_SET_REGISTER and VIDIOC_INT_GET_REGISTER for the
pvrusb2 driver.  This is a debugging aid which will not be enabled
unless CONFIG_VIDEO_ADV_DEBUG has been enabled.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>