Fix typo.

Change-Id: Ib21b4df67d4d6fde08f3d80763b16c6e8618859d
diff --git a/src/api.c b/src/api.c
index c7f5848..b43c24fc 100644
--- a/src/api.c
+++ b/src/api.c
@@ -640,7 +640,7 @@
 
 			/* Take target vCPU out of mailbox recv_waiter list. */
 			/*
-			 * TODO: Consider using a double-linked list for the
+			 * TODO: Consider using a doubly-linked list for the
 			 * receive waiter list to avoid the linear search here.
 			 */
 			struct vcpu **previous_next_pointer =