dmaengine: edma: remove duplicate kfree

fixing of freeing descriptor memory was applied twice, so remove the one
duplicate

Reported-by: Wing-Keung Wang <wingkeung.wang@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/edma.c

@@ -428,7 +428,6 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
 			if (echan->slot[i] < 0) {
 				kfree(edesc);
 				dev_err(dev, "Failed to allocate slot\n");
-				kfree(edesc);
 				return NULL;
 			}
 		}