wifi: iwlwifi: mvm/mld: report non-HT frames as 20 MHz

wifi: iwlwifi: mvm/mld: report non-HT frames as 20 MHz

Non-HT frames can only be encoded in 20 MHz, however, they
could be duplicated on all/some of the subchannels (mostly
used for RTS/CTS), in which case the firmware will report
and estimate of the overall used bandwidth based on energy
detected. This could be confusing so don't report it that
way, always use 20 MHz for non-HT/legacy frames instead.

Note that currently the value doesn't appear to be used by
mac80211, it never checks the bandwidth field for legacy
encodings.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20251019114304.23e6695039ca.I3da7c542bde6de4362755f200248dbcc12aa246e@changeid