cfg80211: fix WoWLAN wakeup tracing

If the device reports a non-wireless wakeup reason, the
tracing code crashes trying to dereference a NULL pointer.
Fix this by checking the pointer on all accesses and also
add a non_wireless tag to the event.

Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>