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/imx-sdma.c b/drivers/dma/imx-sdma.c
index bf736ad..49aa4e87 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -267,7 +267,6 @@
 	struct dma_chan			chan;
 	spinlock_t			lock;
 	struct dma_async_tx_descriptor	desc;
-	dma_cookie_t			last_completed;
 	enum dma_status			status;
 	unsigned int			chn_count;
 	unsigned int			chn_real_count;
@@ -529,7 +528,7 @@
 	else
 		sdmac->status = DMA_SUCCESS;
 
-	sdmac->last_completed = sdmac->desc.cookie;
+	sdmac->chan.completed_cookie = sdmac->desc.cookie;
 	if (sdmac->desc.callback)
 		sdmac->desc.callback(sdmac->desc.callback_param);
 }
@@ -1127,7 +1126,7 @@
 
 	last_used = chan->cookie;
 
-	dma_set_tx_state(txstate, sdmac->last_completed, last_used,
+	dma_set_tx_state(txstate, chan->completed_cookie, last_used,
 			sdmac->chn_count - sdmac->chn_real_count);
 
 	return sdmac->status;