mac80211: allow driver to impose WoWLAN restrictions

If the driver can't support WoWLAN in the current
state, this patch allows it to return 1 from the
suspend callback to do the normal deconfiguration
instead of using suspend/resume calls. Note that
if it does this, resume won't be called.

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