watchdog: core: fix trivial typo in a comment

Let's have balanced round brackets.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/watchdog_core.c

@@ -104,7 +104,7 @@ static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  * timeout module parameter (if it is valid value) or the timeout-sec property
  * (only if it is a valid value and the timeout_parm is out of bounds).
  * If none of them are valid then we keep the old value (which should normally
- * be the default timeout value.
+ * be the default timeout value).
  *
  * A zero is returned on success and -EINVAL for failure.
  */