drm/i915/tc: rename mtl_tc_port_get_pin_assignment_mask()

This function doesn't really return the pin assignment mask, but the
max lane count derived from that.  So rename the function to
mtl_tc_port_get_max_lane_count() to better reflect what it really does.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230825081638.275795-2-luciano.coelho@intel.com