partially revert "x86/mm: Clean IOMMU flags from p2m-pt code"

partially revert "x86/mm: Clean IOMMU flags from p2m-pt code"

This partially reverts commit
854a49a7486a02edae5b3e53617bace526e9c1b1 by re-adding the logic that
propagates changes to the domain physmap done by p2m_pt_set_entry into
the iommu page tables. Without this logic changes to the guest physmap
are not propagated to the iommu, leaving stale iommu entries that can
leak data, or failing to add new entries.

Note that this commit doesn't re-introduce iommu flags to the cpu page
table entries, since the logic to add/remove entries to the iommu page
tables is based on the p2m type and the mfn.

Fixes: 854a49a7486a02 ('x86/mm: Clean IOMMU flags from p2m-pt code')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Alexandru Isaila <aisaila@bitdefender.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>