Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c
index 97e0ae4..c4063b7 100644
--- a/arch/powerpc/kernel/perf_event.c
+++ b/arch/powerpc/kernel/perf_event.c
@@ -759,7 +759,7 @@
 
 	/*
 	 * If group events scheduling transaction was started,
-	 * skip the schedulability test here, it will be peformed
+	 * skip the schedulability test here, it will be performed
 	 * at commit time(->commit_txn) as a whole
 	 */
 	if (cpuhw->group_flag & PERF_EVENT_TXN)