xfrm: use xfrm_addr_cmp() instead of compare addresses directly

Clean up to use xfrm_addr_cmp() instead of compare addresses directly.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>