It is a serious bug if the domain is still mapped to any DTEs when it is
freed as we immediately start freeing page table memory, so any remaining
HW touch will UAF.

If it is not mapped then dev_list is empty and amd_iommu_domain_update()
does nothing.

Remove it and add a WARN_ON() to catch this class of bug.
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4-v2-831cdc4d00f3+1a315-amd_iopgtbl_jgg@nvidia.comSigned-off-by: Joerg Roedel <jroedel@suse.de>