ibcore: Add support for RDMA/RoCE using VLAN(4) devices.

Classify VLAN devices as ethernet in rdma_copy_addr().
This fixes the following error message:

rdma_bind_addr: No such file or directory

Submitted by: Piotr Kubaj <pkubaj@FreeBSD.org>
Differential Revision: https://reviews.freebsd.org/D36120
Sponsored by: NVIDIA Networking

(cherry picked from commit 57af517ac4e8f88339ad1ff778d3b7ac32827430)