Fix the incorrect call to memset in app/memcmp, causing undefined beh…

…avior

The memset call did effectively nothing because it set zero bytes.

app/memcmp/main.c

@@ -154,7 +154,7 @@ void register_signal_handler(int signo)
     struct sigaction act, old_act;
 
     /* Specify #PF handler with signinfo arguments */
-    memset(&act, sizeof(sigaction), 0);
+    memset(&act, 0, sizeof(sigaction));
     act.sa_sigaction = fault_handler;
     act.sa_flags = SA_RESTART | SA_SIGINFO;