wifi: cfg80211: default S1G chandef width to 1MHz

wifi: cfg80211: default S1G chandef width to 1MHz

When management frames are passed down to be transmitted by usermode, often
times the NL80211_ATTR_CHANNEL_WIDTH is not used as its implied to be
transmitted on the control width. This can lead to errors during chandef
validation as the offsets from the channel center are wrong. Ensure we
initialise S1G chandefs to a width of 1MHz rather then 20MHz.

Signed-off-by: Lachlan Hodges <lachlan.hodges@morsemicro.com>
Link: https://patch.msgid.link/20251021061201.235754-1-lachlan.hodges@morsemicro.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>