[ar7] move acx-mac80211 to the ar7 generic target

None of the AC49x boards that we support actually have Wi-Fi.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@34208 3c298f89-4303-0410-b956-a3cf2f4a3e73

[ar7] create generic subtarget

Signed-off-by: Daniel Golle <dgolle@allnet.de>
Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@34147 3c298f89-4303-0410-b956-a3cf2f4a3e73