wcn36xx: Enable hardware scan offload for 5Ghz band

Until now, offload scanning for 5Ghz channels was considered broken.
However it was mostly a driver issue, caused by bad reporting of the
beacons/probe-resp bands and frequencies, which has been fixed.

We can now allow offload scan for 5GHz band, this reduces the scanning
time comparing to software driven scanning.

Note that offloaded scan is limited to 48 channels, check for this.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1634554678-7993-2-git-send-email-loic.poulain@linaro.org