mac80211: Clear wowlan flag when drv_suspend returns failure

drv_resume can get called without a prior call to drv_suspend.
Consider the following steps:

1. Suspend is started but driver's drv_suspend returns error.
2. Suspend is aborted. local->wowlan flag is left set.
3. Interface is removed.
4. Suspend again. This time open_count is 0 so drv_suspend is
   not called and local->wowlan not cleared.
5. On resume ieee80211_reconfig will call drv_resume since
   local->wowlan is set.

Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>