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/at_hdmac.c b/drivers/dma/at_hdmac.c
index f4aed5f..6baf5d7 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -269,7 +269,7 @@
 	dev_vdbg(chan2dev(&atchan->chan_common),
 		"descriptor %u complete\n", txd->cookie);
 
-	atchan->completed_cookie = txd->cookie;
+	atchan->chan_common.completed_cookie = txd->cookie;
 
 	/* move children to free_list */
 	list_splice_init(&desc->tx_list, &atchan->free_list);
@@ -1016,14 +1016,14 @@
 
 	spin_lock_irqsave(&atchan->lock, flags);
 
-	last_complete = atchan->completed_cookie;
+	last_complete = chan->completed_cookie;
 	last_used = chan->cookie;
 
 	ret = dma_async_is_complete(cookie, last_complete, last_used);
 	if (ret != DMA_SUCCESS) {
 		atc_cleanup_descriptors(atchan);
 
-		last_complete = atchan->completed_cookie;
+		last_complete = chan->completed_cookie;
 		last_used = chan->cookie;
 
 		ret = dma_async_is_complete(cookie, last_complete, last_used);
@@ -1129,7 +1129,7 @@
 	spin_lock_irqsave(&atchan->lock, flags);
 	atchan->descs_allocated = i;
 	list_splice(&tmp_list, &atchan->free_list);
-	atchan->completed_cookie = chan->cookie = 1;
+	chan->completed_cookie = chan->cookie = 1;
 	spin_unlock_irqrestore(&atchan->lock, flags);
 
 	/* channel parameters */
@@ -1329,7 +1329,7 @@
 		struct at_dma_chan	*atchan = &atdma->chan[i];
 
 		atchan->chan_common.device = &atdma->dma_common;
-		atchan->chan_common.cookie = atchan->completed_cookie = 1;
+		atchan->chan_common.cookie = atchan->chan_common.completed_cookie = 1;
 		list_add_tail(&atchan->chan_common.device_node,
 				&atdma->dma_common.channels);