CVE-2023-53482 iommu: Fix error unwind in iommu_group_alloc()

In the Linux kernel, the following vulnerability has been resolved: iommu: Fix error unwind in iommugroupalloc If either iommugroupgratefile fails then the iommugroup is leaked. Destroy it on these error paths. Found by kselftest/iommu/iommufdfailnth...