iommu/amd: Don't copy GCR3 table root pointer

When iommu is pre_enabled in kdump kernel, if a device is set up with
guest translations (DTE.GV=1), then don't copy GCR3 table root pointer
but move the device over to an empty guest-cr3 table and handle the
faults in the PPR log (which answer them with INVALID). After all these
PPR faults are recoverable for the device and we should not allow the
device to change old-kernels data when we don't have to.

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>