On AIX, we don't need to be aware of any change on the protocol stack of
Linux kernel.

Change-Id: Ib8b14fa930acddb3bc720d401271e8daf567b784
Reviewed-on: https://go-review.googlesource.com/c/157298
Run-TryBot: Mikio Hara <mikioh.public.networking@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>