ath10k: fix device initialization routine

Hardware CUS232 version 2 has some issues with cold
reset that lead to Data Bus Errors or system hangs
in some cases. It's safer to use warm reset when
possible as it shouldn't trigger the
aforementioned issues.

Prefer warm reset over cold reset. However since
warm reset doesn't work after FW crash make sure to
fallback to cold reset when booting up the HW.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Marek Puzyniak <marek.puzyniak@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>