The mt8192 iommu support 0~16GB iova. We separate it to four banks:
0~4G; 4G~8G; 8G~12G; 12G~16G.

The "dma-ranges" could be used to adjust the bank we locate.
If we don't set this property. The default range always is 0~4G.

This is optional and only needed in mt8192, the dma ranges should
not cross 4G/8G/12G.

Here we don't have actual bus/parent concept here.  And the iova
requirement is for our HW. Thus put the property in our node.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Irui Wang <irui.wang@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>