xfrm: checkpatch erros with space prohibited

Fix checkpatch error "space prohibited xxx".

Signed-off-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index e50be42..3348566 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1824,7 +1824,7 @@
 	struct net *net = sock_net(skb->sk);
 	struct xfrm_state *x;
 	struct km_event c;
-	int err = - EINVAL;
+	int err = -EINVAL;
 	u32 mark = 0;
 	struct xfrm_mark m;
 	struct xfrm_aevent_id *p = nlmsg_data(nlh);