ARM: dts: rockchip: Enable Cortex-A12 HW PMU events on rk3288

This adds the dts node for the PMU with the correct PMUIRQ interrupts
for each core.

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>