p54spi: Fix workqueue deadlock

priv->work must not be synced while priv->mutex is locked, because
the mutex is taken in the work handler.
Move cancel_work_sync down to after the device shutdown code.
This is safe, because the work handler checks fw_state and bails out
early in case of a race.

Signed-off-by: Michael Buesch <m@bues.ch>
Cc: <stable@vger.kernel.org>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/p54spi.c

@@ -588,15 +588,15 @@ static void p54spi_op_stop(struct ieee80211_hw *dev)
 
 	WARN_ON(priv->fw_state != FW_STATE_READY);
 
-	cancel_work_sync(&priv->work);
-
 	p54spi_power_off(priv);
 	spin_lock_irqsave(&priv->tx_lock, flags);
 	INIT_LIST_HEAD(&priv->tx_pending);
 	spin_unlock_irqrestore(&priv->tx_lock, flags);
 
 	priv->fw_state = FW_STATE_OFF;
 	mutex_unlock(&priv->mutex);
+
+	cancel_work_sync(&priv->work);
 }
 
 static int __devinit p54spi_probe(struct spi_device *spi)