wcn36xx: handle new hal response format

wcn3620 has a new message structure for the reply to some hal
commands.  This patch adds the struct and helper routine that
uses it if the chip is wcn3620, or falls back to the old
helper routine.

We don't know what to do with the candidate list he sends back,
but we can at least accept and ignore it nicely instead of dying.

Signed-off-by: Andy Green <andy.green@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>