csky/perf: Remove driver-specific throttle support

The throttle support has been added in the generic code. Remove
the driver-specific throttle support.

Besides the throttle, perf_event_overflow may return true because of
event_limit. It already does an inatomic event disable. The pmu->stop
is not required either.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20250520181644.2673067-13-kan.liang@linux.intel.com

Author: Kan Liang

arch/csky/kernel/perf_event.c

@@ -1139,8 +1139,7 @@ static irqreturn_t csky_pmu_handle_irq(int irq_num, void *dev)
 		perf_sample_data_init(&data, 0, hwc->last_period);
 		csky_pmu_event_set_period(event);
 
-		if (perf_event_overflow(event, &data, regs))
-			csky_pmu_stop_event(event);
+		perf_event_overflow(event, &data, regs);
 	}
 
 	csky_pmu_enable(&csky_pmu.pmu);