wcn36xx: Add wcn36xx_set_default_rates_v1

Add a routine to set some additional default parameters associated with the
V1 data structure.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200910150552.2178882-2-bryan.odonoghue@linaro.org