packet-infiniband: added support for RoCE-v2 (RRocE)

Added support for the new Routable RDMA over Converged Ethernet.

Change-Id: I97bc29fdc92bdcb12888f38383107a965837963e
Reviewed-on: https://code.wireshark.org/review/3723
Petri-Dish: Evan Huus <eapache@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Evan Huus <eapache@gmail.com>