mac80211: fix channel type recalculation with HT and non-HT interfaces

When running an AP interface along with the cooked monitor interface created
by hostapd, adding an interface and deleting it again triggers a channel type
recalculation during which the (non-HT) monitor interface takes precedence
over the HT AP interface, thus causing the channel type to be set to non-HT.
Fix this by ensuring that a more wide channel type will not be overwritten
by a less wide channel type.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>