dt-bindings: add vendor Monolithic Power Systems

MPS produce power regulators like the MP8859.
Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -617,6 +617,8 @@ patternProperties:
     description: Moxa Inc.
   "^mpl,.*":
     description: MPL AG
+  "^mps,.*":
+    description: Monolithic Power Systems Inc.
   "^mqmaker,.*":
     description: mqmaker Inc.
   "^mscc,.*":