amd-iommu: resume cleanup

Now that enable_iommus() will call iommu_disable() for each iommu,
the call to disable_iommus() during resume is redundant.  Also, the order
for an invalidation is to invalidate device table entries first, then
domain translations.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>