CVE-2026-98282: powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba

In the Linux kernel, the following vulnerability has been resolved:

powerpc/iommu: Fix the overflow validation in iommutcecheckioba

The commit b1af23d836f8 ("KVM: PPC: iommu: Unify TCE checking") unified IOBA parameter checking across KVM and VFIO into iommutcecheckioba(). While doing so, the passed in argument npages is ignored and constant value '1' is used leaving out a possible overflow as the callers can legitimately be using npages > 1 for HSTUFFTCE or HPUTTCEINDIRECT cases.

Fix this by accounting for 'npages', checking for arithmetic overflow, and verifying that the entire requested range (ioba - offset + npages) does not exceed the table capacity 'size'.