drm/i915/tc: Handle non-TC encoders when getting the pin assignment

drm/i915/tc: Handle non-TC encoders when getting the pin assignment

For consistency, handle the case where
intel_tc_port_get_pin_assignment() is called for a non-TypeC encoder,
returning the default NONE pin assignment value, similarly to how this
is done in intel_tc_port_max_lane_count().

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://lore.kernel.org/r/20250805073700.642107-16-imre.deak@intel.com
Signed-off-by: Imre Deak <imre.deak@intel.com>