watchdog: Add kernel-doc for wdt_set_timeout()

The wdt_set_timeout function lacked a complete kernel-doc
description. This patch adds missing parameter and return
value descriptions in accordance with kernel-doc standards.

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Guenter Roeck <linux@roeckus.net>
Link: https://lore.kernel.org/r/20240206093857.62444-1-yang.lee@linux.alibaba.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>