mpc512x_dma: remove useless use of lock

Accordingly to dma_cookie_status() description locking is not required.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>

drivers/dma/mpc512x_dma.c

@@ -556,15 +556,7 @@ static enum dma_status
 mpc_dma_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	       struct dma_tx_state *txstate)
 {
-	struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
-	enum dma_status ret;
-	unsigned long flags;
-
-	spin_lock_irqsave(&mchan->lock, flags);
-	ret = dma_cookie_status(chan, cookie, txstate);
-	spin_unlock_irqrestore(&mchan->lock, flags);
-
-	return ret;
+	return dma_cookie_status(chan, cookie, txstate);
 }
 
 /* Prepare descriptor for memory to memory copy */