drm/i915/display: reduce the includes in intel_dvo_dev.h

Only include what's needed.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/8523aa88daaf2dbf0ce138980142dbcd6d1ae0bc.1667383630.git.jani.nikula@intel.com