Linux 4.1 is also affected from the dma issue, so remove the dma
proprties there as well.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46599 3c298f89-4303-0410-b956-a3cf2f4a3e73