wifi: ath12k: fix recovery fail while firmware crash when doing channel switch

When firmware crashed while channel switch running, recovery starts in
ath12k. Then ieee80211_sta_connection_lost() will be called by function
ieee80211_restart_work() in mac80211. And then many WMI command timeout
because firmware is crashed. Each WMI command cost 3 seconds, then the
total time will be large and leads recovery fail.

Hence change to set value ATH12K_FLAG_CRASH_FLUSH early and then
ath12k_wmi_cmd_send() will not wait 3 seconds, then recovery will be
started quickly and success.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4

Signed-off-by: Wen Gong <quic_wgong@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230905105229.10090-1-quic_wgong@quicinc.com