rstp: Remove old code from set_port_id__().
rstp: Use rstp_times_equal() to compare struct rstp_times.
rstp: Rename rstp_priority_vector_is_superior() into compare_rstp_priority_vector().
      Merge SUPERIOR_ABSOLUTE and SUPERIOR_SAME_DES.
rstp: Remove old code from compare_rstp_priority_vector().
      Add comment to compare_rstp_priority_vector() function.
rstp: Delete get_id_string_from_uint8_t() function.
rstp: Remove bit shifts from rstp states.