iommu/ipmmu-vmsa: Use iommu_device_sysfs_add()/remove()

Extend the driver to make use of iommu_device_sysfs_add()/remove()
functions to hook up initial sysfs support.

Suggested-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Joerg Roedel <jroedel@suse.de>