iommu: Clear iommu-dma ops on cleanup

In the Linux kernel, the following vulnerability has been resolved: iommu: Clear iommu-dma ops on cleanup If iommu_device_register() encounters an error, it can end up tearing down already-configured groups and default domains, however this currently still leaves devices hooked up to iommu-dma (and even historically the behaviour in this area was at best inconsistent across architectures/drivers...) Although in the case that an IOMMU is present whose driver has failed to probe, users cannot necessarily expect DMA to work anyway, it's still arguable that we should do our best to put things back as if the IOMMU driver was never there at all, and certainly the potential for crashing in iommu-dma itself is undesirable. Make sure we clean up the dev->dma_iommu flag along with everything else.