perf: Fix the nr_addr_filters fix

Thomas reported that commit 652ffc2 ("perf/core: Fix narrow
startup race when creating the perf nr_addr_filters sysfs file") made
the entire attribute group vanish, instead of only the nr_addr_filters
attribute.

Additionally a stray return.

Insufficient coffee was involved with both writing and merging the
patch.

Fixes: 652ffc2 ("perf/core: Fix narrow startup race when creating the perf nr_addr_filters sysfs file")
Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Link: https://lkml.kernel.org/r/20231122100756.GP8262@noisy.programming.kicks-ass.net

Author: Peter Zijlstra

kernel/events/core.c

@@ -11417,12 +11417,10 @@ static umode_t pmu_dev_is_visible(struct kobject *kobj, struct attribute *a, int
 	struct device *dev = kobj_to_dev(kobj);
 	struct pmu *pmu = dev_get_drvdata(dev);
 
-	if (!pmu->nr_addr_filters)
+	if (n == 2 && !pmu->nr_addr_filters)
 		return 0;
 
 	return a->mode;
-
-	return 0;
 }
 
 static struct attribute_group pmu_dev_attr_group = {