net/9p: remove unused p9_req_t aux field

The p9_req_t field 'aux' has not been used in a very long time,
remove leftover field declaration

Link: http://lkml.kernel.org/r/1580941152-12973-1-git-send-email-asmadeus@codewreck.orgSigned-off-by: Dominique Martinet <dominique.martinet@cea.fr>

include/net/9p/client.h

@@ -73,7 +73,6 @@ enum p9_req_status_t {
  * @wq: wait_queue for the client to block on for this request
  * @tc: the request fcall structure
  * @rc: the response fcall structure
- * @aux: transport specific data (provided for trans_fd migration)
  * @req_list: link for higher level objects to chain requests
  */
 struct p9_req_t {
@@ -83,7 +82,6 @@ struct p9_req_t {
 	wait_queue_head_t wq;
 	struct p9_fcall tc;
 	struct p9_fcall rc;
-	void *aux;
 	struct list_head req_list;
 };