ath10k: handle IEEE80211_CHANCTX_CHANGE_WIDTH properly

Vdevs associated with a given chanctx should be
restarted if the bandwidth changes. Otherwise
traffic may cease.

This is known to fix STA CSA with bandwidths wider
than 20MHz.

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