wcn36xx: Add Host suspend indication support

In order to activate ipv4 ARP offload, ipv6 NS offload and firmware GTK
offload we need to send a unidirectional indication from host to wcn
indicating a transition to suspend.

Once done, firmware will respond to ARP broadcasts, ipv6 NS lookups and
perform GTK rekeys without waking the host.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Tested-by: Benjamin Li <benl@squareup.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210605011140.2004643-11-bryan.odonoghue@linaro.org