Fix incorrect SubTLV values and properly handle both old and new
variant of TRILL Version SubTLV

Note that the SubTLV values have not changed in RFC7176.

Bug: 10387
Change-Id: I452debb7165e70f31f1a3a19a44c488c5bbdb959
Reviewed-on: https://code.wireshark.org/review/3661
Reviewed-by: Evan Huus <eapache@gmail.com>