mlx4: Add infrastructure for selecting VFs to enable QP0 via MLX proxy QPs

mlx4: Add infrastructure for selecting VFs to enable QP0 via MLX proxy QPs

This commit adds the infrastructure for enabling selected VFs to
operate SMI (QP0) MADs without restriction.

Additionally, for these enabled VFs, their QP0 proxy and tunnel QPs
are MLX QPs.  As such, they operate over VL15.  Therefore, they are
not affected by "credit" problems or changes in the VLArb table (which
may shut down VL0).

Non-enabled VFs may only create UD proxy QP0 qps (which are forced by
the hypervisor to send packets using the q-key it assigns and places
in the qp-context).  Thus, non-enabled VFs will not pose a security
risk.  The hypervisor discards any privileged MADs it receives from
these non-enabled VFs.

By default, all VFs are NOT enabled, and must explicitly be enabled
by the administrator.

The sysfs interface which operates the VF enablement infrastructure
is provided in the next commit.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>