drm/i915/dvo: move DVO chip types to intel_dvo.c

Reduce clutter from intel_drv.h with the minimal change.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/95203dbf844061da95f33614d0cb61533a11fdd4.1556809195.git.jani.nikula@intel.com