RDMA/mlx5: Enable vport loopback when user context or QP mandate

A user can create a QP which can accept loopback traffic, but that's not
enough. We need to enable loopback on the vport as well. Currently vport
loopback is enabled only when more than 1 users are using the IB device,
update the logic to consider whatever a QP which supports loopback was
created, if so enable vport loopback even if there is only a single user.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>