drm/i915/tc: Move the intel_tc_port struct declaration to intel_tc.c

Move the intel_tc_port struct to intel_tc.c for better isolation. This
requires allocating the struct dynamically.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-8-imre.deak@intel.com