fsldma: implement a private tx_list

Drop fsldma's use of tx_list from struct dma_async_tx_descriptor in
preparation for removal of this field.

Cc: Li Yang <leoli@freescale.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/fsldma.h

@@ -90,6 +90,7 @@ struct fsl_dma_ld_hw {
 struct fsl_desc_sw {
 	struct fsl_dma_ld_hw hw;
 	struct list_head node;
+	struct list_head tx_list;
 	struct dma_async_tx_descriptor async_tx;
 	struct list_head *ld;
 	void *priv;