arm: dts: allwinner: H3: Add PMU node

Add the Performance Monitoring Unit (PMU) device tree node to the H3
.dtsi, which tells DT users which interrupts are triggered by PMU
overflow events on each core. The numbers come from the manual and have
been checked in U-Boot and with perf in Linux.

Tested with perf record and taskset on an OrangePi Zero.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>