wcn36xx: add missing 5GHz channels 136 and 144

The official feature-complete WCN3680B driver (known as prima, open source
but not upstream) supports channels 136 and 144.

However, these channels are missing in upstream. Add them here to get
closer to feature parity with prima.

Signed-off-by: Benjamin Li <benl@squareup.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211025175359.3591048-3-benl@squareup.com