[XFRM] xfrm_policy_destroy: Rename and relative fixes.

Since __xfrm_policy_destroy is used to destory the resources
allocated by xfrm_policy_alloc. So using the name
__xfrm_policy_destroy is not correspond with xfrm_policy_alloc.
Rename it to xfrm_policy_destroy.

And along with some instances that call xfrm_policy_alloc
but not using xfrm_policy_destroy to destroy the resource,
fix them.

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 6424e53..35fc16a 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1043,7 +1043,7 @@
 	return xp;
  error:
 	*errp = err;
-	kfree(xp);
+	xfrm_policy_destroy(xp);
 	return NULL;
 }