wifi: iwlwifi: mvm: fix sched scan IE sizing

wifi: iwlwifi: mvm: fix sched scan IE sizing

Scheduled scan built the probe request before iwl_mvm_scan_fits(),
so oversized IEs could be copied into the fixed preq buffer before
length validation. Move iwl_mvm_build_scan_probe() after the fits
check.

Also advertise max_sched_scan_ie_len using iwl_mvm_max_scan_ie_len()
so userspace limits account for driver-inserted DS/TPC bytes.

Assisted-by: GitHubCopilot:gpt-5.3-codex
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Link: https://patch.msgid.link/20260714141909.53d2722c79e7.Iebb922efa6173c92f14cd8aa8b4e7f372c0a0fb7@changeid
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>