Fixes https://github.com/freifunk-gluon/gluon/issues/311

gluon-ebtables-filter-multicast: allow hop-by-hop options as ICMPv6 is sometimes prefixed by an HBH header

the ports were interchanged, see the following packet flow:

client:546 --> [ff02::1:2]:547
server:547 --> client:546

therefore we need to allow outgoing multicast packets with dst-port 547
and unicast packets from bat0 to clients with dst-port 546 and 547 in the other direction