iommu/mediatek: Convert to probe/release_device() call-backs

Convert the Mediatek IOMMU driver to use the probe_device() and
release_device() call-backs of iommu_ops, so that the iommu core code
does the group and sysfs setup.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200429133712.31431-23-joro@8bytes.org


Signed-off-by: Joerg Roedel <jroedel@suse.de>