iommu/mediatek: add support for mtk iommu generation one HW

Mediatek SoC's M4U has two generations of HW architcture. Generation one
uses flat, one layer pagetable, and was shipped with ARM architecture, it
only supports 4K size page mapping. MT2701 SoC uses this generation one
m4u HW. Generation two uses the ARM short-descriptor translation table
format for address translation, and was shipped with ARM64 architecture,
MT8173 uses this generation two m4u HW. All the two generation iommu HW
only have one iommu domain, and all its iommu clients share the same
iova address.

These two generation m4u HW have slit different register groups and
register offset, but most register names are the same. This patch add iommu
support for mediatek SoC mt2701.

Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>