dts:mc3: Set I2C_1 clock to 400 kHz

All devices on the bus support at least full speed (400 kHz).
Increase the clock to speed-up the communication.

arch/arm64/boot/dts/seconorth/mc3.dtsi

@@ -371,7 +371,7 @@ &aud2htx {
 };
 
 &i2c1 {
-	clock-frequency = <100000>;
+	clock-frequency = <400000>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_i2c1>;
 	status = "okay";