dmaengine: Add might_sleep() to dmaengine_synchronize()

Implementations of dmaengine_synchronize() are allowed to sleep, hence the
function must not be called to from atomic context. Add might_sleep() to
dmaengine_synchronize() to make it easier to detect non-compliant callers.
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

include/linux/dmaengine.h

@@ -895,6 +895,8 @@ static inline int dmaengine_terminate_async(struct dma_chan *chan)
  */
 static inline void dmaengine_synchronize(struct dma_chan *chan)
 {
+	might_sleep();
+
 	if (chan->device->device_synchronize)
 		chan->device->device_synchronize(chan);
 }