cfg80211/mac80211: enable proper device_set_wakeup_enable handling

In WoWLAN, we only get the triggers when we actually get
to suspend. As a consequence, drivers currently don't
know that the device should enable wakeup. However, the
device_set_wakeup_enable() API is intended to be called
when the wakeup is enabled, not later when needed.

Add a new set_wakeup() call to cfg80211 and mac80211 to
allow drivers to properly call device_set_wakeup_enable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>