IB/mlx5: Extend CQ creation to get uar page index from user space

Extend CQ creation to get uar page index from user space, this mode can be
used with the UAR dynamic mode APIs to allocate/destroy a UAR object.

Link: https://lore.kernel.org/r/20200324060143.1569116-3-leon@kernel.org
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Reviewed-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>