dmaengine: add dmaengine_prep_dma_sg() helper

This was only prep API which didnt have an helper
Signed-off-by: NVinod Koul <vinod.koul@intel.com>

include/linux/dmaengine.h

@@ -755,6 +755,16 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
 	return chan->device->device_prep_interleaved_dma(chan, xt, flags);
 }
 
+static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_sg(
+		struct dma_chan *chan,
+		struct scatterlist *dst_sg, unsigned int dst_nents,
+		struct scatterlist *src_sg, unsigned int src_nents,
+		unsigned long flags)
+{
+	return chan->device->device_prep_dma_sg(chan, dst_sg, dst_nents,
+			src_sg, src_nents, flags);
+}
+
 static inline int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
 {
 	if (!chan || !caps)