Add missing includes.

Change-Id: Iaa130c0a7eb2cbc0c8486546e5b622661b6d9e23
diff --git a/init/watchdogd.c b/init/watchdogd.c
index fb53836..7f64fc4 100644
--- a/init/watchdogd.c
+++ b/init/watchdogd.c
@@ -18,6 +18,7 @@
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <linux/watchdog.h>