async_tx: export async_tx_quiesce

Replace open coded "wait and acknowledge" instances with async_tx_quiesce.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
index eb640f0..9f0e7bd 100644
--- a/include/linux/async_tx.h
+++ b/include/linux/async_tx.h
@@ -152,4 +152,6 @@
 async_trigger_callback(enum async_tx_flags flags,
 	struct dma_async_tx_descriptor *depend_tx,
 	dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+void async_tx_quiesce(struct dma_async_tx_descriptor **tx);
 #endif /* _ASYNC_TX_H_ */