dmaengine: dma_issue_pending_all == nop when CONFIG_DMA_ENGINE=n

The device list will always be empty in this configuration, so no need
to walk the list.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

include/linux/dmaengine.h

@@ -390,11 +390,16 @@ static inline enum dma_status dma_async_is_complete(dma_cookie_t cookie,
 enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
 #ifdef CONFIG_DMA_ENGINE
 enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
+void dma_issue_pending_all(void);
 #else
 static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
 {
 	return DMA_SUCCESS;
 }
+static inline void dma_issue_pending_all(void)
+{
+	do { } while (0);
+}
 #endif
 
 /* --- DMA device --- */
@@ -403,7 +408,6 @@ int dma_async_device_register(struct dma_device *device);
 void dma_async_device_unregister(struct dma_device *device);
 void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
 struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
-void dma_issue_pending_all(void);
 #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
 struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
 void dma_release_channel(struct dma_chan *chan);