dt-bindings: mailbox: tegra: Document Tegra234 HSP

Add the compatible string for the HSP block found on the Tegra234 SoC.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/mailbox/nvidia,tegra186-hsp.yaml

@@ -57,6 +57,9 @@ properties:
     oneOf:
       - const: nvidia,tegra186-hsp
       - const: nvidia,tegra194-hsp
+      - items:
+          - const: nvidia,tegra234-hsp
+          - const: nvidia,tegra194-hsp
 
   reg:
     maxItems: 1