hw/virtio/virtio-iommu: Enforce power-of-two notify for both MAP and UNMAP

Currently we only enforce power-of-two mappings (required by the QEMU
notifier) for UNMAP requests. A MAP request not aligned on a
power-of-two may be successfully handled by VFIO, and then the
corresponding UNMAP notify will fail because it will attempt to split
that mapping. Ensure MAP and UNMAP notifications are consistent.

Fixes: dde3f08b ("virtio-iommu: Handle non power of 2 range invalidations")
Reported-by: Tina Zhang <tina.zhang@intel.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-Id: <20220718135636.338264-1-jean-philippe@linaro.org>
Tested-by: Tina Zhang <tina.zhang@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>