memory: Add IOMMUTLBEvent

memory: Add IOMMUTLBEvent

This way we can tell between regular IOMMUTLBEntry (entry of IOMMU
hardware) and notifications.

In the notifications, we set explicitly if it is a MAPs or an UNMAP,
instead of trusting in entry permissions to differentiate them.

Signed-off-by: Eugenio Pérez <[email protected]>
Reviewed-by: Peter Xu <[email protected]>
Reviewed-by: Juan Quintela <[email protected]>
Acked-by: Jason Wang <[email protected]>
Message-Id: <20201116165506[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Matthew Rosato <[email protected]>
Acked-by: David Gibson <[email protected]>