dmaengine: zxdma: fix memset call

Fix the call to memset in this driver
[linux-4.2-next-20150911/drivers/dma/zx296702_dma.c:444]: (warning)
memset() called to fill 0 bytes of 'ds'.
Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/zx296702_dma.c

@@ -441,7 +441,7 @@ static struct zx_dma_desc_sw *zx_alloc_desc_resource(int num,
 		kfree(ds);
 		return NULL;
 	}
-	memset(ds->desc_hw, sizeof(struct zx_desc_hw) * num, 0);
+	memset(ds->desc_hw, 0, sizeof(struct zx_desc_hw) * num);
 	ds->desc_num = num;
 	return ds;
 }