dmaengine: fix memleak in dma_async_device_unregister

While debugging a dma driver I noticed a memleak after
unloading the driver module.

Caught by kmemleak.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 6f51a0a..e7a3230 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -826,6 +826,7 @@
 		chan->dev->chan = NULL;
 		mutex_unlock(&dma_list_mutex);
 		device_unregister(&chan->dev->device);
+		free_percpu(chan->local);
 	}
 }
 EXPORT_SYMBOL(dma_async_device_unregister);