wcn36xx: Add ipv4 ARP offload support in suspend

Add ARP offload support. Firmware is capable of responding to ARP requests
for a single ipv4 address only.

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/20210605011140.2004643-4-bryan.odonoghue@linaro.org