ARM: dts: exynos: Remove not accurate secondary ADC compatible

The Exynos3250 ADC has its own compatible because of differences from
other Exynos SoCs.  Therefore it is not entirely compatible with
samsung,exynos-adc-v2.  Remove the samsung,exynos-adc-v2.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

arch/arm/boot/dts/exynos3250.dtsi

@@ -450,8 +450,7 @@ pdma1: pdma@12690000 {
 		};
 
 		adc: adc@126c0000 {
-			compatible = "samsung,exynos3250-adc",
-				     "samsung,exynos-adc-v2";
+			compatible = "samsung,exynos3250-adc";
 			reg = <0x126C0000 0x100>;
 			interrupts = <GIC_SPI 137 IRQ_TYPE_LEVEL_HIGH>;
 			clock-names = "adc", "sclk";