wcn36xx: Correct band/freq reporting on RX

For packets originating from hardware scan, the channel and band is
included in the buffer descriptor (bd->rf_band & bd->rx_ch).

For 2Ghz band the channel value is directly reported in the 4-bit
rx_ch field. For 5Ghz band, the rx_ch field contains a mapping
index (given the 4-bit limitation).

The reserved0 value field is also used to extend 4-bit mapping to
5-bit mapping to support more than 16 5Ghz channels.

This change adds correct reporting of the frequency/band, that is
used in scan mechanism. And is required for 5Ghz hardware scan
support.

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/1634554678-7993-1-git-send-email-loic.poulain@linaro.org