priv->path_cost and priv->priority can only be set as GObject properties,
which already does the same range check. Hence, the checks are never reached.

This also avoids a compiler warning:

    libnm-core/nm-setting-bridge-port.c: In function ‘verify’:
    libnm-core/nm-setting-bridge-port.c:132:22: error: comparison is always false due to limited range of data type [-Werror=type-limits]
      if (priv->path_cost > BR_MAX_PATH_COST) {
                          ^