watchdog: fix watchdog-test.c build warning

Fix compiler warning by making the function static:

Documentation/watchdog/src/watchdog-test.c:34:6: warning: no previous prototype for 'term'
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/src/watchdog-test.c

@@ -31,7 +31,7 @@ static void keep_alive(void)
  * or "-e" to enable the card.
  */
 
-void term(int sig)
+static void term(int sig)
 {
     close(fd);
     fprintf(stderr, "Stopping watchdog ticks...\n");