s390: Fix misspellings in comments

Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/perf_cpum_cf.c

@@ -383,7 +383,7 @@ static int __hw_perf_event_init(struct perf_event *event)
 
 	/* Validate the counter that is assigned to this event.
 	 * Because the counter facility can use numerous counters at the
-	 * same time without constraints, it is not necessary to explicity
+	 * same time without constraints, it is not necessary to explicitly
 	 * validate event groups (event->group_leader != event).
 	 */
 	err = validate_event(hwc);

arch/s390/kernel/perf_event.c

@@ -238,7 +238,7 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry,
 	dump_trace(__perf_callchain_kernel, entry, NULL, regs->gprs[15]);
 }
 
-/* Perf defintions for PMU event attributes in sysfs */
+/* Perf definitions for PMU event attributes in sysfs */
 ssize_t cpumf_events_sysfs_show(struct device *dev,
 				struct device_attribute *attr, char *page)
 {