dmaengine: add private header file

Add a local private header file to contain definitions and declarations
which should only be used by DMA engine drivers.

We also fix linux/dmaengine.h to use LINUX_DMAENGINE_H to guard against
multiple inclusion.

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/mxs-dma.c b/drivers/dma/mxs-dma.c
index 3696e6e..daa84ee 100644
--- a/drivers/dma/mxs-dma.c
+++ b/drivers/dma/mxs-dma.c
@@ -28,6 +28,8 @@
 #include <mach/dma.h>
 #include <mach/common.h>
 
+#include "dmaengine.h"
+
 /*
  * NOTE: The term "PIO" throughout the mxs-dma implementation means
  * PIO mode of mxs apbh-dma and apbx-dma.  With this working mode,