[IPV6]: Fix route.c gcc-3.4.x inlining error.

Fixes the inline error when compiling net/ipv6/route.c with gcc-3.4.1
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: David S. Miller <davem@redhat.com>

net/ipv6/route.c

@@ -584,7 +584,7 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
 /* Protected by rt6_lock.  */
 static struct dst_entry *ndisc_dst_gc_list;
 static int ipv6_get_mtu(struct net_device *dev);
-static inline unsigned int ipv6_advmss(unsigned int mtu);
+static unsigned int ipv6_advmss(unsigned int mtu);
 
 struct dst_entry *ndisc_dst_alloc(struct net_device *dev, 
 				  struct neighbour *neigh,