s1gw: fix ParamEnbId: fix charstring pattern for 'enb-conn'Permit IPv6 addresses by including hexadecimal characters.Change-Id: Ie95fb6ca53c1fa305bc7501173102a8a7265fa38Related: osmo-s1gw.git I112283b140a070924d59935a3bdd6fd63fc8c7ea