ARM: dts: clean up arm-pmu node for exynos4

This patch cleans a arm-pmu node up for exynos4. Only exynos4412 series
boards have four pmu interrupts. Rest of exynos4 boards, except 4412, have only
two pmu interrupts. Thus, we can define two interrupts in the
exynos4.dtsi and extends the interrupts only exynos4412.dtsi.

Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Tested-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>