Documentation/: fix warnings from -Wmissing-prototypes in HOSTCFLAGS

Fix up -Wmissing-prototypes in compileable userspace code, mainly under
Documentation/.

Signed-off-by: Ladinu Chandrasinghe <ladinu.pub@gmail.com>
Signed-off-by: Trevor Keith <tsrk@tsrk.net>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/watchdog/src/watchdog-test.c b/Documentation/watchdog/src/watchdog-test.c
index 65f6c19..a750532 100644
--- a/Documentation/watchdog/src/watchdog-test.c
+++ b/Documentation/watchdog/src/watchdog-test.c
@@ -18,7 +18,7 @@
  * the PC Watchdog card to reset its internal timer so it doesn't trigger
  * a computer reset.
  */
-void keep_alive(void)
+static void keep_alive(void)
 {
     int dummy;