RDMA/mlx5: Remove ncont from mlx5_ib_cont_pages()

This is the same as ib_umem_num_dma_blocks(umem, 1UL << page_shift), have
the callers compute it directly.

Link: https://lore.kernel.org/r/20201026131936.1335664-7-leon@kernel.org


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