ARM: dts: imx28-evk: Run I2C0 at 400kHz

It is safe to operate I2C0 at 400kHz as SGTL5000 supports this frequency.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx28-evk.dts

@@ -193,6 +193,7 @@
 			i2c0: i2c@80058000 {
 				pinctrl-names = "default";
 				pinctrl-0 = <&i2c0_pins_a>;
+				clock-frequency = <400000>;
 				status = "okay";
 
 				sgtl5000: codec@0a {