Use the address supplied by user when creating a child interface.

Previously, the address requested by the user was ignored and overridden
with parent's GID and the random QP number assigned to the child.

Link: https://lore.kernel.org/r/20200623110105.1225750-3-leon@kernel.orgSigned-off-by: Michael Guralnik <michaelgur@mellanox.com>
Reviewed-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>