gluon-mesh-batman-adv: enable bridge learning on bat0 again

Reverts d5829d8 ("gluon-mesh-batman-adv-core: disable bridge port
learning on bat0").

Fixes #1121

package/gluon-mesh-batman-adv-core/luasrc/lib/gluon/upgrade/310-gluon-mesh-batman-adv-core-mesh

@@ -43,19 +43,11 @@ uci:section('network', 'interface', 'bat0',
		    proto = 'none',
		    macaddr = sysconfig.primary_mac,
		    multicast_router = 2,
		    learning = 0,
		    learning = 1,
	    }
)

uci:delete('network', 'client_lan')
if sysconfig.lan_ifname then
	uci:section('network', 'interface', 'client_lan',
		    {
			    unicast_flood = 0,
		    }
	)
	uci:set('network', 'client_lan', 'ifname', sysconfig.lan_ifname)
end

uci:save('network')