drm/i915/tc: Check for TC PHY explicitly in intel_tc_port_fia_max_lane_count()

Check explicitly if the port passed to
intel_tc_port_fia_max_lane_count() has a TC PHY, instead of relying on
the default TC mode value set for non-TC PHY ports.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-7-imre.deak@intel.com