dmaengine: Remove unused define for dma_request_slave_channel_reason()

No users left in the kernel, it can be removed.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200828084141.14902-1-peter.ujfalusi@ti.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

include/linux/dmaengine.h

@@ -1527,8 +1527,6 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
 }
 #endif
 
-#define dma_request_slave_channel_reason(dev, name) dma_request_chan(dev, name)
-
 static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
 {
 	struct dma_slave_caps caps;