dmaengine: provide a common function for completing a dma descriptor

Provide a common function to do the cookie mechanics for completing
a DMA descriptor.

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/imx-dma.c

@@ -66,7 +66,7 @@ static void imxdma_handle(struct imxdma_channel *imxdmac)
 {
 	if (imxdmac->desc.callback)
 		imxdmac->desc.callback(imxdmac->desc.callback_param);
-	imxdmac->chan.completed_cookie = imxdmac->desc.cookie;
+	dma_cookie_complete(&imxdmac->desc);
 }
 
 static void imxdma_irq_handler(int channel, void *data)