iommufd/iova_bitmap: Remove iterator logic

iommufd/iova_bitmap: Remove iterator logic

The newly introduced dynamic pinning/windowing greatly simplifies the code
and there's no obvious performance advantage that has been identified that
justifies maintinaing both schemes.

Remove the iterator logic and have iova_bitmap_for_each() just invoke the
callback with the total iova/length.

Fixes: 2780025e01e2 ("iommufd/iova_bitmap: Handle recording beyond the mapped pages")
Link: https://lore.kernel.org/r/20240627110105.62325-12-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Matt Ochs <mochs@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>