wifi: iwlwifi: scan: correctly check if PSC listen period is needed

The flags variable is incorrectly checked while it is still cleared and
has not been assigned any value yet.
Fix it.

Fixes: a615323f

 ("wifi: iwlwifi: mvm: always apply 6 GHz probe limitations")
Signed-off-by: Ayala Beker <ayala.beker@intel.com>
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240605140556.291c33f9a283.Id651fe69828aebce177b49b2316c5780906f1b37@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>