RDMA/mlx5: Use rdma_umem_for_each_dma_block()

Replace an open coding of rdma_umem_for_each_dma_block() with the proper
function.

Fixes: b3d47ebd ("RDMA/mlx5: Use mlx5_umr_post_send_wait() to update MR pas")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v1-c13a5b88359b+556d0-mlx5_umem_block_jgg@nvidia.com


Reviewed-by: Devesh Sharma <devesh.s.sharma@oracle.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>