xfrm: do not reset secpath for xfrm interface after policy validation

Partial revert of b0355dbbf13c ("Fix XFRM-I support for nested ESP tunnels")
because secpath is not available in netfilter forward chain for xfrm
interface.
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 5c61ec0..47d3a48 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3745,9 +3745,6 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 			goto reject;
 		}
 
-		if (if_id)
-			secpath_reset(skb);
-
 		xfrm_pols_put(pols, npols);
 		return 1;
 	}