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>
diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index 9a3cbac..6731f19 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -153,16 +153,7 @@
 					    dma_cookie_t cookie,
 					    struct dma_tx_state *txstate)
 {
-	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
-	dma_cookie_t last_used;
-	enum dma_status ret;
-
-	last_used = chan->cookie;
-
-	ret = dma_async_is_complete(cookie, chan->completed_cookie, last_used);
-	dma_set_tx_state(txstate, chan->completed_cookie, last_used, 0);
-
-	return ret;
+	return dma_cookie_status(chan, cookie, txstate);
 }
 
 static dma_cookie_t imxdma_tx_submit(struct dma_async_tx_descriptor *tx)