wl1251: use to_delayed_work()

Use to_delayed_work() instead of open-coding it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
[Update commit message]
Signed-off-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ti/wl1251/ps.c

@@ -32,7 +32,7 @@ void wl1251_elp_work(struct work_struct *work)
 	struct delayed_work *dwork;
 	struct wl1251 *wl;
 
-	dwork = container_of(work, struct delayed_work, work);
+	dwork = to_delayed_work(work);
 	wl = container_of(dwork, struct wl1251, elp_work);
 
 	wl1251_debug(DEBUG_PSM, "elp work");