dt-bindings: Add MP2856/MP2857 voltage regulator device

Monolithic Power Systems, Inc. (MPS) MP2856/MP2857
dual-loop, digital, multi-phase controller.
Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231211160519.21254-2-potin.lai.pt@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/trivial-devices.yaml

@@ -117,6 +117,10 @@ properties:
           - fsl,mpl3115
             # MPR121: Proximity Capacitive Touch Sensor Controller
           - fsl,mpr121
+            # Monolithic Power Systems Inc. multi-phase controller mp2856
+          - mps,mp2856
+            # Monolithic Power Systems Inc. multi-phase controller mp2857
+          - mps,mp2857
             # Monolithic Power Systems Inc. multi-phase controller mp2888
           - mps,mp2888
             # Monolithic Power Systems Inc. multi-phase controller mp2971