trivial: drop unused 802.3 code if we compile without IPX

(originally from http://wohnheim.fh-wedel.de/~joern/software/kernel/je/25/)
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>