dt-bindings: host1x: Add iommu-map property

Add schema information for specifying context stream IDs. This uses
the standard iommu-map property.
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml

@@ -144,6 +144,11 @@ allOf:
         reset-names:
           maxItems: 1
 
+        iommu-map:
+          description: Specification of stream IDs available for memory context device
+            use. Should be a mapping of IDs 0..n to IOMMU entries corresponding to
+            usable stream IDs.
+
       required:
         - reg-names