usb: dwc3: clean up redundant parameter comment

@list is not as a parameter of dwc3_event_buffer, so remove it in
comments.
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.h

@@ -367,7 +367,6 @@ struct dwc3_trb;
 
 /**
  * struct dwc3_event_buffer - Software event buffer representation
- * @list: a list of event buffers
  * @buf: _THE_ buffer
  * @length: size of this buffer
  * @lpos: event offset