drm/i915/bios: save a higher level pointer in ddi_vbt_port_info[]

We'll be needing the intel_bios_encoder_data pointer going forward, and
it's just easier to store the higher level pointer in the
ddi_vbt_port_info[] array.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/89717516e99afccfecf1a7c6c938b8349f65e985.1615998927.git.jani.nikula@intel.com