iommufd/iova_bitmap: Check iova_bitmap_done() after set ahead

iommufd/iova_bitmap: Check iova_bitmap_done() after set ahead

After iova_bitmap_set_ahead() returns it may be at the end of the range.
Move iova_bitmap_set_ahead() earlier to avoid unnecessary attempt in
trying to pin the next pages by reusing iova_bitmap_done() check.

Fixes: 2780025e01e2 ("iommufd/iova_bitmap: Handle recording beyond the mapped pages")
Link: https://lore.kernel.org/r/20240627110105.62325-7-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>