ARM: EXYNOS: Add arm-pmu DT binding for exynos5250

This patch enables arm-pmu to bind device tree for exynos5250. The exynos5250
has two pmus which have combiner irq type.
Reviewed-by: NThomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: NChanho Park <chanho61.park@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos5250.dtsi

@@ -109,6 +109,12 @@
 		};
 	};
 
+	pmu {
+		compatible = "arm,cortex-a15-pmu";
+		interrupt-parent = <&combiner>;
+		interrupts = <1 2>, <22 4>;
+	};
+
 	watchdog {
 		compatible = "samsung,s3c2410-wdt";
 		reg = <0x101D0000 0x100>;