wcn36xx: Encode PHY mode for 80MHz channel in hw_value

This commit encodes the 802.11ac PHY mode for a given channel in the upper
bits of the hw_value field. This allows for a neat read-out and application
of the relevant PHY setting.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200910150708.2179043-5-bryan.odonoghue@linaro.org