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/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 7e640bf..c59c4f0 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -258,6 +258,7 @@
  * struct dma_chan - devices supply DMA channels, clients use them
  * @device: ptr to the dma device who supplies this channel, always !%NULL
  * @cookie: last cookie value returned to client
+ * @completed_cookie: last completed cookie for this channel
  * @chan_id: channel ID for sysfs
  * @dev: class device for sysfs
  * @device_node: used to add this to the device chan list
@@ -269,6 +270,7 @@
 struct dma_chan {
 	struct dma_device *device;
 	dma_cookie_t cookie;
+	dma_cookie_t completed_cookie;
 
 	/* sysfs */
 	int chan_id;