kernel: fix typo

Change-Id: I5a9e53100dcac9b78cae655c3c68444357832094
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
diff --git a/kernel/unified/sched.c b/kernel/unified/sched.c
index ce999ac..bea7779 100644
--- a/kernel/unified/sched.c
+++ b/kernel/unified/sched.c
@@ -288,7 +288,7 @@
 
 	K_DEBUG("thread %p for %d ns\n", _current, duration);
 
-	/* wait of 0 ns is treated as a 'yield' */
+	/* wait of 0 ms is treated as a 'yield' */
 	if (duration == 0) {
 		k_yield();
 		return;