drm/i915: Store DVO SRCDIM register offset under intel_dvo_device

Store the DVO SRCDIM register offset alongside the DVO control register
offset in intel_dvo_device. This gets rid of the switch statement whose
case values are the DVO control register offsets. Such a construct would
cause problems for register type safety.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446672017-24497-12-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>