[BUG] dts: hi6220: PMU events not fully functional

[Carlton Shepherd]

Hello,

The perf subsystem does not detect any PMU events for the HiSilicon
6220 SoC. (Tested on a HiKey 620 with 5.17.0-rc1.)

Based on [1] and [2], /arch/arm64/boot/dts/hisilicon/hi6220.dtsi is
missing a PMU node. This was patched for the hi3660 in
/arch/arm64/boot/dts/hisilicon/hi3660.dtsi [3], but remains defective
for the hi6220.

Could somebody please provide some assistance?

Kind regards,
Carlton Shepherd

1. https://www.96boards.org/documentation/consumer/hikey/hikey960/support/pmu-on-hikey960.md.html
2. https://discuss.96boards.org/t/linux-perf-list-failing-to-detect-hardware-events-on-hikey620/11752
3. https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1465696.html