net: Rename net/nexthop.h net/rtnh.h

The header contains rtnh_ macros so rename the file accordingly.
Allows a later patch to use the nexthop.h name for the new
nexthop code.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -59,7 +59,7 @@
 #include <net/xfrm.h>
 #include <net/netevent.h>
 #include <net/netlink.h>
-#include <net/nexthop.h>
+#include <net/rtnh.h>
 #include <net/lwtunnel.h>
 #include <net/ip_tunnels.h>
 #include <net/l3mdev.h>