[S390] hwsampler: allow cpu hotplug

The hardware sample cpu hotplug notifier always returns NOTIFY_BAD.
That will prevent cpu hotplug if the machine is enabled for hardware
sampling even if it is not used. Fix the cpu hotplug notifier and
allow cpu hotplug if hardware sampling is unused.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/oprofile/hwsampler.c

@@ -580,7 +580,7 @@ static int hws_cpu_callback(struct notifier_block *nfb,
 {
 	/* We do not have sampler space available for all possible CPUs.
 	   All CPUs should be online when hw sampling is activated. */
-	return NOTIFY_BAD;
+	return (hws_state <= HWS_DEALLOCATED) ? NOTIFY_OK : NOTIFY_BAD;
 }
 
 static struct notifier_block hws_cpu_notifier = {