Fix bnxt build in LINT

LINT includes bnxt_re driver. Adjust the path in files, add missing
files and add a new BNXT_C to build (which thinly wraps OFED version
with bnxt specicif stuff).

Sponsored by: Netflix
Fixes: acd884dec99a ("RDMA/bnxt_re: Add bnxt_re RoCE driver")

bnxt_{en/re}: Update bnxt_en and bnxt_re Makefile

Reviewed by: imp
Approved by: imp
Differential revision: https://reviews.freebsd.org/D45202

RDMA/bnxt_re: Add bnxt_re RoCE driver

This patch introduces the RoCE driver for the
Broadcom NetXtreme-E 10/25/50/100/200G RoCE HCAs.

The RoCE driver is a two part driver that relies
on the bnxt_en NIC driver to operate. The changes
needed in the bnxt_en driver is included through
another patch "L2-RoCE driver communication interface"
in this set.

Presently, There is no user space support, Hence
recommendation to use the krping kernel module for
testing. User space support will be incorporated in
subsequent patch submissions.

Reviewed by: imp
Approved by: imp
Differential revision: https://reviews.freebsd.org/D45011