RDMA/mlx5: Use set_mkc_access_pd_addr_fields() in reg_create()

reg_create() open codes this helper, use the shared code.

Link: https://lore.kernel.org/r/20200914112653.345244-3-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>