dmaengine/amba-pl08x: Complete doc comment for struct pl08x_txd

Doc comment for struct pl08x_txd was incomplete. Complete that.
Signed-off-by: NViresh Kumar <viresh.kumar@st.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>

include/linux/amba/pl08x.h

@@ -105,8 +105,16 @@ struct pl08x_phy_chan {
 
 /**
  * struct pl08x_txd - wrapper for struct dma_async_tx_descriptor
+ * @tx: async tx descriptor
+ * @node: node for txd list for channels
+ * @src_addr: src address of txd
+ * @dst_addr: dst address of txd
+ * @len: transfer len in bytes
+ * @direction: direction of transfer
  * @llis_bus: DMA memory address (physical) start for the LLIs
  * @llis_va: virtual memory address start for the LLIs
+ * @cctl: control reg values for current txd
+ * @ccfg: config reg values for current txd
  */
 struct pl08x_txd {
 	struct dma_async_tx_descriptor tx;