drm/i915: s/tc_port/hpd_pin/ in icp+ TC hotplug bits

Parametrize the icp+ TC HPD bits using hpd_pin rather than
tc_port so it's clear what kind of an animal we're dealing
with.

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/20201028213323.5423-12-ville.syrjala@linux.intel.com