cfg80211: retrieve S1G operating channel number

When retrieving the S1G channel number from IEs, we should retrieve
the operating channel instead of the primary channel. The S1G operation
element specifies the main channel of operation as the oper channel,
unlike for HT and HE which specify their main channel of operation as
the primary channel.

Signed-off-by: Kieran Frewen <kieran.frewen@morsemicro.com>
Signed-off-by: Bassem Dawood <bassem@morsemicro.com>
Link: https://lore.kernel.org/r/20220420041321.3788789-1-kieran.frewen@morsemicro.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>