RDMA/mlx5: Use mlx5_umr_post_send_wait() to update xlt

RDMA/mlx5: Use mlx5_umr_post_send_wait() to update xlt

Move mlx5_ib_update_mr_pas logic to umr.c, and use
mlx5_umr_post_send_wait() instead of mlx5_ib_post_send_wait().

Since it is the last use of mlx5_ib_post_send_wait(), remove it.

Link: https://lore.kernel.org/r/55a4972f156aba3592a2fc9bcb33e2059acf295f.1649747695.git.leonro@nvidia.com
Signed-off-by: Aharon Landau <aharonl@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>