dmaengine: consolidate tx_status functions

Now that we have the completed cookie in the dma_chan structure, we
can consolidate the tx_status functions by providing a function to set
the txstate structure and returning the DMA status.  We also provide
a separate helper to set the residue for cookies which are still in
progress.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
[imx-sdma.c & mxs-dma.c]
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/mpc512x_dma.c

@@ -557,17 +557,14 @@ 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;
-	dma_cookie_t last_used;
-	dma_cookie_t last_complete;
 
 	spin_lock_irqsave(&mchan->lock, flags);
-	last_used = mchan->chan.cookie;
-	last_complete = mchan->chan.completed_cookie;
+	ret = dma_cookie_status(chan, cookie, txstate);
 	spin_unlock_irqrestore(&mchan->lock, flags);
 
-	dma_set_tx_state(txstate, last_complete, last_used, 0);
-	return dma_async_is_complete(cookie, last_complete, last_used);
+	return ret;
 }
 
 /* Prepare descriptor for memory to memory copy */