SUNRPC: Remove comment for sp_lock

It is obsolete since sp_lock was discarded in commit 580a2575
("SUNRPC: discard sp_lock").
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/svc_xprt.c

@@ -46,7 +46,6 @@ static LIST_HEAD(svc_xprt_class_list);
 
 /* SMP locking strategy:
  *
- *	svc_pool->sp_lock protects most of the fields of that pool.
  *	svc_serv->sv_lock protects sv_tempsocks, sv_permsocks, sv_tmpcnt.
  *	when both need to be taken (rare), svc_serv->sv_lock is first.
  *	The "service mutex" protects svc_serv->sv_nrthread.