qtnfmac: implement scan timeout

Userspace tools may hang on scan in the case when scan completion event
is not returned by firmware. This patch implements the scan timeout
to avoid such situation.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>
Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Avinash Patil <avinashp@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>