vfio/type1: sanitize for overflow using check_*_overflow()

Adopt check_*_overflow() functions to clearly express overflow check
intent.

Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Fixes: 73fa0d10 ("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-v6-1-2542b96bcc8e@fb.com


Signed-off-by: Alex Williamson <alex@shazbot.org>