IB/mlx5: Fix configuration of port capabilities

When the "ib_virt" cap is set, configuration of port capabilities need
to be done through mlx5_core_modify_hca_vport_context.
Since modify_hca_vport_context accepts mask and value, there is no need
to read the port capabilities and calculate the new cap values so we
avoid the mutex when ib_virt is set.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>