[][kernel][mt7988][cpu][Add PMU node to dts]

[Description]
Add PMU node to dts.

If without this patch, perf cannot monitor CPU hardware
events.

[Release-log]
N/A


Change-Id: I8b1ed2da4a8f6c810a86b6f1ee2c0a35851d7dba
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6855313
1 file changed