dt-bindings: dma: arm,pl330: Add missing 'iommus' property

The pl330 can be behind an IOMMU which is the case for Arm Juno board.
Add the 'iommus' property allowing for 1 IOMMU entry per channel for
writes and 1 IOMMU entry for reads.
Signed-off-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220801210237.1501488-1-robh@kernel.orgSigned-off-by: NVinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/arm,pl330.yaml

@@ -55,6 +55,12 @@ properties:
 
   dma-coherent: true
 
+  iommus:
+    minItems: 1
+    maxItems: 9
+    description: Up to 1 IOMMU entry per DMA channel for writes and 1
+      IOMMU entry for reads.
+
   power-domains:
     maxItems: 1