IB/mlx5: Enable UAR to have DevX UID

UID field was added to alloc_uar and dealloc_uar PRM command, to specify
DevX UID for UAR. This change enables firmware validating user access to
its own UAR resources.

For the kernel allocated UARs the UID will stay 0 as of today.

Signed-off-by: Meir Lichtinger <meirl@nvidia.com>
Reviewed-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>