Declare watchdog functions in watchdog.h

These functions are only available for powerpc and are not declared in a
header file. We want to use the rest function in two places (board_f and
board_r), so declare the functions in watchdog.h.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sh/lib/board.c b/arch/sh/lib/board.c
index 34d7881..6e43acf 100644
--- a/arch/sh/lib/board.c
+++ b/arch/sh/lib/board.c
@@ -65,6 +65,7 @@
 #if defined(CONFIG_WATCHDOG)
 extern int watchdog_init(void);
 extern int watchdog_disable(void);
+# undef INIT_FUNC_WATCHDOG_INIT
 # define INIT_FUNC_WATCHDOG_INIT	watchdog_init,
 # define WATCHDOG_DISABLE       	watchdog_disable
 #else