drm/radeon/kms: Add specific rs690 authorized register table

rs690 is r3xx 3D engine with AVIVO modesetting so we need to allow
AVIVO register for vline synchronization. This add a specific table
to rs690 to handle that. Thanks to Marc (marvin24) for debugging
this and kudos to Andre (taiu1) for spotting the origin of the bugs.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>