drivers: nrf_wifi: Rejig the statistics

Separate out host(local) and FW(remote) statistics and in case of a
FW statistics timeout, return success with a magic value in the FW
statistics, this way atleast host statistics would be handy for
debugging instead of sending failure up.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>