watchdog: gef_wdt: include fs.h

Add missing include "linux/fs.h".
This fixes compile failure.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/gef_wdt.c

@@ -30,6 +30,7 @@
 #include <linux/module.h>
 #include <linux/miscdevice.h>
 #include <linux/watchdog.h>
+#include <linux/fs.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>