rstp: Use uint8_t instead of unsigned char for network structs.
rstp: Use OVS_NOT_REACHED() instead of ovs_assert(0).
rstp: Fix memory leaks in tx_rstp(), tx_config() and tx_tcn().
rstp: Remove if statement from better_or_same_info().
rstp: rstp_state_name() and rstp_port_role_name() return 'const char *'.
      Remove 'char *temp' from br_refresh_rstp_status() and
      port_refresh_rstp_status().