staging: rtl8712: fix double lock bug in SetPSModeWorkItemCallback()

Fix a double lock bug in SetPSModeWorkItemCallback().

Fixes: 5c2ba8b85e35 ("rtl8712: pwrctrl_priv: Replace semaphore lock with mutex")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl871x_pwrctrl.c

@@ -145,7 +145,7 @@ static void SetPSModeWorkItemCallback(struct work_struct *work)
 		mutex_lock(&pwrpriv->mutex_lock);
 		if (pwrpriv->pwr_mode == PS_MODE_ACTIVE)
 			r8712_set_rpwm(padapter, PS_STATE_S4);
-		mutex_lock(&pwrpriv->mutex_lock);
+		mutex_unlock(&pwrpriv->mutex_lock);
 	}
 }