ARC: HSDK: wireup perf irq

Newer version of HSDK aka HSDK-4xD (with dual issue HS48x4 CPU) wired up
the perf interrupt, so enable that in DT.
This is OK for old HSDK where this irq is ignored because pct irq is not
wired up in hardware.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>