[NET]: linux/if_tr.h needs asm/byteorder.h

<linux/if_tr.h> uses __be16, but does not directly include
<asm/byteorder.h>.  Add this in, so that dhcp/net-tools token ring code
can compile again.

Signed-off-by: Tom Rini <trini@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>