ARM: dts: fix incorrect ak8975 compatible for exynos4412-trats2 board

This patch fixed incorrect compatible for ak8975 magnetic sensor.
ak8975 magnetic sensor use compatible "ak8975" or "asahi-kasei,ak8975"
In this patch, use "asahi-kasei,ak8975" according to dt bindings document.
Signed-off-by: Beomho Seo <beomho.seo@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos4412-trats2.dts

@@ -503,7 +503,7 @@ i2c_ak8975: i2c-gpio-0 {
 		status = "okay";
 
 		ak8975@0c {
-			compatible = "ak,ak8975";
+			compatible = "asahi-kasei,ak8975";
 			reg = <0x0c>;
 			gpios = <&gpj0 7 0>;
 		};