dt-bindings: rtc: tegra: Document Tegra234 RTC

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

Documentation/devicetree/bindings/rtc/nvidia,tegra20-rtc.yaml

@@ -27,6 +27,7 @@ properties:
               - nvidia,tegra210-rtc
               - nvidia,tegra186-rtc
               - nvidia,tegra194-rtc
+              - nvidia,tegra234-rtc
           - const: nvidia,tegra20-rtc
 
   reg: