This reverts commit b7118623.

Migration was implemented by QEMU commit:
commit 8cdcf3c1e58d04b6811956d7608efeb66c42d719
Author: Peter Xu <peterx@redhat.com>
Date:   Fri Jan 6 12:06:13 2017 +0800

    intel_iommu: allow migration

https://bugzilla.redhat.com/show_bug.cgi?id=1433994