ath10k: fix idle power consumption

mac80211 can update vif powersave state while
disconnected. Firmware doesn't behave nicely and
consumes more power than necessary if PS is
disabled on a non-started vdev. Hence
force-enable PS for non-running vdevs.

This reduces power drain on QCA61X4 from 88mA to
36mA when interface is up and not associated.
QCA988X wasn't measured.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>