ath6kl: Fix scan related issue on suspend-resume

When a scan request is pending while going to suspend, any new
scan request after resume will fail. So, cancel all scan requests
in all the vifs before moving to suspend state.

Signed-off-by: PingYang Zhang <pingzhan@qca.qualcomm.com>
Signed-off-by: Vivek Natarajan <nataraja@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>