arm: pmu: Fix non-devicetree probing

There is a problem in the non-devicetree PMU probing where some
probe functions may get the number of supported events through
smp_call_function_any() using the arm_pmu supported_cpus mask.
But at the time the probe function is called, the supported_cpus
mask is empty so the call fails. This patch makes sure the mask
is set before calling the init function rather than after.
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/perf/arm_pmu.c

@@ -1010,8 +1010,8 @@ int arm_pmu_device_probe(struct platform_device *pdev,
 		if (!ret)
 			ret = init_fn(pmu);
 	} else {
-		ret = probe_current_pmu(pmu, probe_table);
 		cpumask_setall(&pmu->supported_cpus);
+		ret = probe_current_pmu(pmu, probe_table);
 	}
 
 	if (ret) {