perf: Fix function pointer case

With the advent of CFI it is no longer acceptible to cast function
pointers.

The robot complains thusly:

  kernel-events-core.c:warning:cast-from-int-(-)(struct-perf_cpu_pmu_context-)-to-remote_function_f-(aka-int-(-)(void-)-)-converts-to-incompatible-function-type
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

kernel/events/core.c

@@ -1119,6 +1119,11 @@ static int perf_mux_hrtimer_restart(struct perf_cpu_pmu_context *cpc)
 	return 0;
 }
 
+static int perf_mux_hrtimer_restart_ipi(void *arg)
+{
+	return perf_mux_hrtimer_restart(arg);
+}
+
 void perf_pmu_disable(struct pmu *pmu)
 {
 	int *count = this_cpu_ptr(pmu->pmu_disable_count);
@@ -11270,8 +11275,7 @@ perf_event_mux_interval_ms_store(struct device *dev,
 		cpc = per_cpu_ptr(pmu->cpu_pmu_context, cpu);
 		cpc->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
 
-		cpu_function_call(cpu,
-			(remote_function_f)perf_mux_hrtimer_restart, cpc);
+		cpu_function_call(cpu, perf_mux_hrtimer_restart_ipi, cpc);
 	}
 	cpus_read_unlock();
 	mutex_unlock(&mux_interval_mutex);