IPv6: Fix inconsistencies in the printing of some option names

[tcpdump] / tests / ipv6hdr-heapoverflow-v.out

    1  1995-08-15 05:27:12.808464432 IP6 (class 0x33, flowlabel 0x03030, hlim 48, next-header HBH (0), payload length 12336) 3030:3030:3030:3030:3030:3030:3030:3030 > 3030:3030:3030:3030:3030:3030:3030:3030: HBH  [|hbh]