Add the PCI write end padding flag to device_cap_flags enum and set it
during mlx5_ib_query_device so it will be reported to user-space.

During WQ/QP creation, set that capability for WQ/QP if user requested
it and HW supports it.

PCI write end padding modification is not supported for now. There's no
such flag for a QP but for a WQ, create and modify use the same flag.
Return an error if PCI write end padding flag is set during modify_wq.
Signed-off-by: NNoa Osherovich <noaos@mellanox.com>
Reviewed-by: NMajd Dibbiny <majd@mellanox.com>
Signed-off-by: NLeon Romanovsky <leon@kernel.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>