ar71xx: add missing WZR-450HP2 patch from r43026 for 3.10

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43175 3c298f89-4303-0410-b956-a3cf2f4a3e73