hwmon: (w83793) Saving negative errors in unsigned

"ret" is used to store the return value for watchdog_trigger() and it
should be signed for the error handling to work.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --git a/drivers/hwmon/w83793.c b/drivers/hwmon/w83793.c
index 9de81a4..612807d 100644
--- a/drivers/hwmon/w83793.c
+++ b/drivers/hwmon/w83793.c
@@ -1294,7 +1294,7 @@
 static ssize_t watchdog_write(struct file *filp, const char __user *buf,
 	size_t count, loff_t *offset)
 {
-	size_t ret;
+	ssize_t ret;
 	struct w83793_data *data = filp->private_data;
 
 	if (count) {