wil6210: add support for abort scan

Implement cfg80211 abort_scan op to allow the upper layer to
abort an ongoing scan request.
In addition, notify wil6210 device on scan abort request instead
of just ignoring the scan response.

Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>