wifi: ath12k: fix WARN_ON during ath12k_mac_update_vif_chan

Fix WARN_ON() from ath12k_mac_update_vif_chan() if vdev is not up.
Since change_chanctx can be called even before vdev_up.

Do vdev stop followed by a vdev start in case of vdev is down.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0-02903-QCAHKSWPL_SILICONZ-1

Signed-off-by: Manish Dharanenthiran <quic_mdharane@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230802085852.19821-2-quic_mdharane@quicinc.com