rtc: m41t80: correct kerneldoc function names

Fix the following make W=1 kernel build warnings:

  drivers/rtc/rtc-m41t80.c:811: warning: expecting prototype for wdt_close(). Prototype was for wdt_release() instead
  drivers/rtc/rtc-m41t80.c:830: warning: expecting prototype for notify_sys(). Prototype was for wdt_notify_sys() instead

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210517110641.473386-1-yangyingliang@huawei.com