Don't access i915->vbt.ddi_port_info[] directly.
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c52c39df43374b51f56439daf8047079afae7749.1579270868.git.jani.nikula@intel.com