IB/mlx5: Enable DEVX on IB

IB has additional protections with SELinux that cannot be extended to the
DEVX domain. SELinux can restrict access to pkeys. The first version of
DEVX blocked IB entirely until this could be understood.

Since DEVX requires CAP_NET_RAW, it supersedes the SELinux restriction and
allows userspace to form arbitrary packets with arbitrary pkeys.

Thus we enable IB for DEVX when CAP_NET_RAW is given.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>