mac80211: ignore AP_VLAN in ieee80211_recalc_chanctx_chantype

When bringing down the AP, a WARN_ON is hit because the bss config chandef
is empty here.
Since AP_VLAN channel settings do not matter for anything chanctx related
(always inherits the settings from the AP interface), let's just ignore
it here.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>