drm/i915/bios: use dvi and hdmi support helpers

Improve clarity by using the helpers we have.

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/3a0b52593f19a465dc0dd898db5f6bf13537d734.1654870175.git.jani.nikula@intel.com