dw_dmac: introduce total_len field in struct dw_desc

By this new field we distinguish a total length of the chain and the individual
length of each descriptor in the chain.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h
index 13000d2b..833b4cf 100644
--- a/drivers/dma/dw_dmac_regs.h
+++ b/drivers/dma/dw_dmac_regs.h
@@ -296,6 +296,7 @@
 	struct list_head		tx_list;
 	struct dma_async_tx_descriptor	txd;
 	size_t				len;
+	size_t				total_len;
 };
 
 #define to_dw_desc(h)	list_entry(h, struct dw_desc, desc_node)