In mt8192, we preassign 0-4G; 4G-8G; 8G-12G for different multimedia
engines. This depends on the "dma-ranges=" in the iommu consumer's dtsi
node.
Adds 12G-16G region here. and reword the previous comment. we don't limit
which master locate in which region.
CCU still is 8G-12G. Don't change it here.
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>