One second is not enough for some devices to ackowledge null data frame
which is sent at the end of ap_max_inactivity interval. In particular,
this causes severe Wi-Fi instability with Apple iPhone which may take
up to 3 seconds to respond.
Signed-off-by: Dmitry Ivanov <dima@ubnt.com>
Backport of r47149
git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@47150 3c298f89-4303-0410-b956-a3cf2f4a3e73