ath11k: remove "ath11k_mac_get_ar_vdev_stop_status" references

Unused structure ath11k_vdev_stop_status is removed.
'ath11k_mac_get_ar_vdev_stop_status' api has been replaced
with 'ath11k_mac_get_ar_by_vdev_id' inside vdev_stopped_event.

Signed-off-by: Ritesh Singh <ritesi@codeaurora.org>
Signed-off-by: Maharaja Kennadyrajan <mkenna@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1605514143-17652-4-git-send-email-mkenna@codeaurora.org