dt-bindings: iommu: Add Apple SART DMA address filter

Apple SoCs such as the M1 come with a simple DMA address filter called
SART. Unlike a real IOMMU no pagetables can be configured but instead
DMA transactions can be allowed for up to 16 paddr regions. The consumer
also needs special support since not all DMA allocations have to be
added to this filter.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sven Peter <sven@svenpeter.dev>