route: Mark unused routing attributes as such

Also removes an unused policy entry for an attribute which is
only used in kernel->user direction.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/rtnetlink.h

@@ -267,10 +267,10 @@ enum rtattr_type_t
 	RTA_PREFSRC,
 	RTA_METRICS,
 	RTA_MULTIPATH,
-	RTA_PROTOINFO,
+	RTA_PROTOINFO, /* no longer used */
 	RTA_FLOW,
 	RTA_CACHEINFO,
-	RTA_SESSION,
+	RTA_SESSION, /* no longer used */
 	RTA_MP_ALGO, /* no longer used */
 	RTA_TABLE,
 	__RTA_MAX

net/ipv4/fib_frontend.c

@@ -506,7 +506,6 @@ const struct nla_policy rtm_ipv4_policy[RTA_MAX+1] = {
 	[RTA_PREFSRC]		= { .type = NLA_U32 },
 	[RTA_METRICS]		= { .type = NLA_NESTED },
 	[RTA_MULTIPATH]		= { .len = sizeof(struct rtnexthop) },
-	[RTA_PROTOINFO]		= { .type = NLA_U32 },
 	[RTA_FLOW]		= { .type = NLA_U32 },
 };