ARM: shmobile: lager: fixup IIC2 clock frequency

Current Lager IIC2 is using default clock frequency,
but, ak4643 audio codec chip needs 100kHz
This patch clarifies IIC2 clock frequency as 100kHz.
Signed-off-by: NKuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7790-lager.dts

@@ -429,6 +429,8 @@
 	pinctrl-0 = <&iic2_pins>;
 	pinctrl-names = "default";
 
+	clock-frequency = <100000>;
+
 	composite-in@20 {
 		compatible = "adi,adv7180";
 		reg = <0x20>;