dt-bindings: iio: pressure: meas,ms5611: add max SPI frequency to the example

Added max SPI frequency setting to the example.
Signed-off-by: Mitja Spes <mitja@lxnav.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221021135827.1444793-4-mitja@lxnav.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/pressure/meas,ms5611.yaml

@@ -55,6 +55,7 @@ examples:
             compatible = "meas,ms5611";
             reg = <0>;
             vdd-supply = <&ldo_3v3_gnss>;
+            spi-max-frequency = <20000000>;
         };
     };
 ...