watchdog: watchdog_core.h: make functions extern

Make the functions in watchdog_core.h extern like it should.
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

drivers/watchdog/watchdog_core.h

@@ -29,5 +29,5 @@
 /*
  *	Functions/procedures to be called by the core
  */
-int watchdog_dev_register(struct watchdog_device *);
-int watchdog_dev_unregister(struct watchdog_device *);
+extern int watchdog_dev_register(struct watchdog_device *);
+extern int watchdog_dev_unregister(struct watchdog_device *);