iommu/amd: Restore GA log/tail pointer on host resume

This will give IOMMU GA log a chance to work after resume
from s3/s4.

Fixes: 8bda0cfb

 ("iommu/amd: Detect and initialize guest vAPIC log")

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20211123161038.48009-2-mlevitsk@redhat.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>