ARM: EXYNOS: Add arm-pmu DT binding for exynos421x

This patch adds a arm-pmu node to bind device tree for exynos4210.
The exynos4210 and 4212 have two cpus which includes a pmu. In contrast, the
exynos4412 has 4 cpus and pmus. We need to define two more pmus for this type
board. However, supporting arm-pmu for the exynos4412 will handle it later
because there is no dts support for 4412 based board.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos4210.dtsi

@@ -77,6 +77,12 @@
 		#clock-cells = <1>;
 	};
 
+	pmu {
+		compatible = "arm,cortex-a9-pmu";
+		interrupt-parent = <&combiner>;
+		interrupts = <2 2>, <3 2>;
+	};
+
 	pinctrl_0: pinctrl@11400000 {
 		compatible = "samsung,exynos4210-pinctrl";
 		reg = <0x11400000 0x1000>;