drm/radeon/kms/atom: Fix DVO support

DVO in 12 bit mode (which seems to be the most common
config) requires 2x ppll.

Fixes fdo bug 21857.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
1 file changed