net80211: name IEEE80211_VHTCAP_SUPP_CHAN_WIDTH_{NONE -> NO160}

IEEE80211_VHTCAP_SUPP_CHAN_WIDTH_NONE is confusing as the field does
indicate that the STA does not support 160 (or 80+80) Mhz.
[802.11ac: Table 8-183v-Subfields of the VHT Capabilities Info field]
All the other bits are related to the support of 160Mhz so make it
clear that it does not mean that we do not support any VHT CHAN WIDTH
but merely do not support the optional 160/80+80.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D47837