vfio/type1: move iova increment to unmap_unpin_*() caller

vfio/type1: move iova increment to unmap_unpin_*() caller

Move incrementing iova to the caller of these functions as part of
preparing to handle end of address space map/unmap.

Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Fixes: 73fa0d10d077 ("vfio: Type1 IOMMU implementation")
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Signed-off-by: Alex Mastro <amastro@fb.com>
Link: https://lore.kernel.org/r/20251028-fix-unmap-v6-2-2542b96bcc8e@fb.com
Signed-off-by: Alex Williamson <alex@shazbot.org>