dmaengine: move last completed cookie into generic dma_chan structure

Every DMA engine implementation declares a last completed dma cookie
in their private dma channel structures.  This is pointless, and
forces driver specific code.  Move this out into the common dma_chan
structure.

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/dw_dmac.c b/drivers/dma/dw_dmac.c
index 0e4b5c6..5bd2300 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -249,7 +249,7 @@
 	dev_vdbg(chan2dev(&dwc->chan), "descriptor %u complete\n", txd->cookie);
 
 	spin_lock_irqsave(&dwc->lock, flags);
-	dwc->completed = txd->cookie;
+	dwc->chan.completed_cookie = txd->cookie;
 	if (callback_required) {
 		callback = txd->callback;
 		param = txd->callback_param;
@@ -997,14 +997,14 @@
 	dma_cookie_t		last_complete;
 	int			ret;
 
-	last_complete = dwc->completed;
+	last_complete = chan->completed_cookie;
 	last_used = chan->cookie;
 
 	ret = dma_async_is_complete(cookie, last_complete, last_used);
 	if (ret != DMA_SUCCESS) {
 		dwc_scan_descriptors(to_dw_dma(chan->device), dwc);
 
-		last_complete = dwc->completed;
+		last_complete = chan->completed_cookie;
 		last_used = chan->cookie;
 
 		ret = dma_async_is_complete(cookie, last_complete, last_used);
@@ -1046,7 +1046,7 @@
 		return -EIO;
 	}
 
-	dwc->completed = chan->cookie = 1;
+	chan->completed_cookie = chan->cookie = 1;
 
 	/*
 	 * NOTE: some controllers may have additional features that we
@@ -1474,7 +1474,7 @@
 		struct dw_dma_chan	*dwc = &dw->chan[i];
 
 		dwc->chan.device = &dw->dma;
-		dwc->chan.cookie = dwc->completed = 1;
+		dwc->chan.cookie = dwc->chan.completed_cookie = 1;
 		if (pdata->chan_allocation_order == CHAN_ALLOCATION_ASCENDING)
 			list_add_tail(&dwc->chan.device_node,
 					&dw->dma.channels);