iommu/ipmmu-vmsa: Link IOMMUs and devices in sysfs

As of commit 7af9a5fd ("iommu/ipmmu-vmsa: Use
iommu_device_sysfs_add()/remove()"), IOMMU devices show up under
/sys/class/iommu/, but their "devices" subdirectories are empty.
Likewise, devices tied to an IOMMU do not have an "iommu" backlink.

Make sure all links are created, on both arm32 and arm64.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>