qtnfmac: add support for scan dwell time configuration

Firmware supports scan dwell time tuning for various types of scans.
Enable support for this feature:
- advertise capability to configure channel dwell time to host
- pass scan dwell parameters to wireless card in scan request

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>