drm/i915: Add PORT_TCn aliases to enum port

Since tgl the DDIs have been named A,B,C,TC1,TC2,TC3...
Add the appropriate enum values for the TC DDIs to enum port.

v2: Deal with rkl and dg1

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201028213323.5423-3-ville.syrjala@linux.intel.com