dmaengine: dmatest: fix container_of member in dmatest_callback

The type of arg passed to dmatest_callback is struct dmatest_done.
It refers to test_done in struct dmatest_thread, not done_wait.

Fixes: 6f6a23a213be ("dmaengine: dmatest: move callback wait ...")
Signed-off-by: Yang Shunyong <shunyong.yang@hxt-semitech.com>
Acked-by: Adam Wallis <awallis@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/dmatest.c

@@ -355,7 +355,7 @@ static void dmatest_callback(void *arg)
 {
 	struct dmatest_done *done = arg;
 	struct dmatest_thread *thread =
-		container_of(arg, struct dmatest_thread, done_wait);
+		container_of(done, struct dmatest_thread, test_done);
 	if (!thread->done) {
 		done->done = true;
 		wake_up_all(done->wait);