The WCN3680 has some specific behaviours that we want to capture to
distinguish it from the WCN3620 and WCN3660 respectively.

Add an identifier for this purpose.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200829033846.2167619-2-bryan.odonoghue@linaro.org