drm/i915/tc: remove "fia" from intel_tc_port_fia_max_lane_count()

It is irrelevant for the caller that the max lane count is being
derived from a FIA register, so having "fia" in the function name is
irrelevant.  Rename the function accordingly.

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/20230825081638.275795-5-luciano.coelho@intel.com