backports: always access net/ieee802154/ with make

In the kernel make will always access net/ieee802154/, we should do the
same.

This was changes in the kenrel in this commit:
commit a53d34c3465b8a840f7400932ae1b0a9f9ed6bef
Author: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>
Date:   Wed Jan 15 02:50:40 2014 +0400

    net: move 6lowpan compression code to separate module

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
1 file changed