IB/mlx5: Allocate the per-port Q counter shared when DEVX is supported

The per-port Q counter is some kernel resource and as such may be used by
few UID(s) upon DEVX usage.

To enable using it for QP/RQ when DEVX context is used need to allocate it
with a sharing mode indication to let firmware allows its usage.

The UID = 0xffff was chosen to mark it.

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