wl12xx: sleep instead of wakeup after tx work

commit d05c806 ("wl12xx: rearrange some ELP wake_up/sleep calls")
introduced a bug in which wl1271_ps_elp_wakeup() was called instead
of wl1271_ps_elp_sleep() after completing the tx work.

Reported-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>

drivers/net/wireless/wl12xx/tx.c

@@ -630,7 +630,7 @@ void wl1271_tx_work(struct work_struct *work)
 
 	wl1271_tx_work_locked(wl);
 
-	wl1271_ps_elp_wakeup(wl);
+	wl1271_ps_elp_sleep(wl);
 out:
 	mutex_unlock(&wl->mutex);
 }