wlcore: consider multiple APs when checking active_link_count

Each AP has its own global and broadcast links, so when
checking for active sta count (according to the active_link_count)
we must take them all into account.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>