wifi: mac80211: reject VHT opmode for unsupported channel widths

In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: reject VHT opmode for unsupported channel widths

VHT operating mode notifications are not defined for channel widths below 20 MHz. In particular, 5 MHz and 10 MHz are not valid under the VHT specification and must be rejected.

Without this check, malformed notifications using these widths may reach ieee80211_chan_width_to_rx_bw(), leading to a WARN_ON due to invalid input. This issue was reported by syzbot.

Reject these unsupported widths early in sta_link_apply_parameters() when opmode_notif is used. The accepted set includes 20, 40, 80, 160, and 80+80 MHz, which are valid for VHT. While 320 MHz is not defined for VHT, it is allowed to avoid rejecting HE or EHT clients that may still send a VHT opmode notification.