CVE-2025-21713 powerpc/pseries/iommu: Don't unset window if it was never set

In the Linux kernel, the following vulnerability has been resolved: powerpc/pseries/iommu: Don't unset window if it was never set On pSeries, when user attempts to use the same vfio container used by different iommu group, the spaprtcesetwindow returns -EPERM and the subsequent cleanup leads to t...