usb: xhci: Remove incorrect comments for struct xhci_container_ctx

There is no member called 'dma' in struct xhci_container_ctx. Remove
the comments that mentions it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>

drivers/usb/host/xhci.h

@@ -482,10 +482,9 @@ struct xhci_protocol_caps {
  * @type: Type of context.  Used to calculated offsets to contained contexts.
  * @size: Size of the context data
  * @bytes: The raw context data given to HW
- * @dma: dma address of the bytes
  *
  * Represents either a Device or Input context.  Holds a pointer to the raw
- * memory used for the context (bytes) and dma address of it (dma).
+ * memory used for the context (bytes).
  */
 struct xhci_container_ctx {
 	unsigned type;