net: fix new sunrpc kernel-doc warning

Fix new kernel-doc warning in sunrpc:

Warning(net/sunrpc/xprt.c:196): No description found for parameter 'xprt'
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sunrpc/xprt.c

@@ -187,6 +187,7 @@ EXPORT_SYMBOL_GPL(xprt_load_transport);
 /**
  * xprt_reserve_xprt - serialize write access to transports
  * @task: task that is requesting access to the transport
+ * @xprt: pointer to the target transport
  *
  * This prevents mixing the payload of separate requests, and prevents
  * transport connects from colliding with writes.  No congestion control