ath11k prints "Received scan event for unknown vdev" when doing the
following test:
1. trigger scan
2. wait 0.2 second
3. iw reg set or 11d scan complete from firmware

Reason: When iw reg set or 11d scan complete, the new country code will
be set to the firmware, and the new regdomain info indicated to ath11k,
then the new channel list will be sent to the firmware. The firmware
will cancel the current scan after receiving WMI_SCAN_CHAN_LIST_CMDID
which is used for the new channel list, and the state of ath11k is
ATH11K_SCAN_RUNNING, then ath11k_get_ar_on_scan_abort() returns NULL and
ath11k_scan_event() returns at this point and does not indicate scan
completion to mac80211.

Indicate scan completion to mac80211 and get rid of the "Received scan
event for unknown vdev" print for the above case.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1
Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210914164226.38843-2-jouni@codeaurora.org