RDMA/mlx5: Block delay drop to unprivileged users

RDMA/mlx5: Block delay drop to unprivileged users

commit ba80013fba656b9830ef45cd40a6a1e44707f47a upstream.

It has been discovered that this feature can globally block the RX port,
so it should be allowed for highly privileged users only.

Fixes: 03404e8ae652("IB/mlx5: Add support to dropless RQ")
Link: https://lore.kernel.org/r/20200322124906.1173790-1-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>