[IPV6]: make flowlabel to return an error

This patch makes the flowlab subsystem to return an error code and makes
some cleanup with procfs ifdefs.
The af_inet6 will use the flowlabel init return code to check the initialization
was correct.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 38df94b5..4d91065 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -219,7 +219,7 @@
 						   struct ipv6_txoptions * fopt);
 extern void			fl6_free_socklist(struct sock *sk);
 extern int			ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen);
-extern void			ip6_flowlabel_init(void);
+extern int			ip6_flowlabel_init(void);
 extern void			ip6_flowlabel_cleanup(void);
 
 static inline void fl6_sock_release(struct ip6_flowlabel *fl)