On an open AP when you pull the plug on the AP, if we are not already in
BMPS mode then the firmware will not generate a disconnection event.

Instead we need to monitor for failure to enter BMPS and treat a string of
failures as connection loss.

Secure AP connections don't appear to demonstrate this behavior so the
work-around is limited to open APs only.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211022140447.2846248-2-bryan.odonoghue@linaro.org