xfrm: Pass const arg to xfrm_alg_len and xfrm_alg_auth_len.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/xfrm.h

@@ -1558,12 +1558,12 @@ static inline int xfrm_aevent_is_on(struct net *net)
 }
 #endif
 
-static inline int xfrm_alg_len(struct xfrm_algo *alg)
+static inline int xfrm_alg_len(const struct xfrm_algo *alg)
 {
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
 }
 
-static inline int xfrm_alg_auth_len(struct xfrm_algo_auth *alg)
+static inline int xfrm_alg_auth_len(const struct xfrm_algo_auth *alg)
 {
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
 }