kernel: modules: activate wpan on kernel 4.1

Make wpan depend on not kernel 3.18 so it will get activated on all 
other kernel versions like 4.0 and 4.1.

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


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46276 3c298f89-4303-0410-b956-a3cf2f4a3e73