[IPV6] MIP6: Add Mobility header definition.

Add Mobility header definition for Mobile IPv6.
Based on MIPL2 kernel patch.

This patch was also written by: Antti Tuominen <anttit@tcs.hut.fi>

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 8e6ec60..72bf47b 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -40,6 +40,7 @@
 #define NEXTHDR_ICMP		58	/* ICMP for IPv6. */
 #define NEXTHDR_NONE		59	/* No next header */
 #define NEXTHDR_DEST		60	/* Destination options header. */
+#define NEXTHDR_MOBILITY	135	/* Mobility header. */
 
 #define NEXTHDR_MAX		255