IB/core: Introduce driver QP type

Vendors can implement type of QPs that are not described in the
InfiniBand specification. To still be able to use the IB/core layer
services (e.g. user object management) without tainting this layer with
driver proprietary logic, a new QP type is added - IB_QPT_DRIVER. This
will be a general QP type that the core layer doesn't know about its true nature.
When a command like create_qp() is passed to a hardware driver the extra
data that is required is taken from the driver channel.
Downstream patches from this series will use that QP type in the mlx5
driver.

Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>