wifi: iwlwifi: adapt ND match notif sizing to fixed matches array

wifi: iwlwifi: adapt ND match notif sizing to fixed matches array

Switch iwl_scan_offload_match_info::matches to a fixed-size array and
adjust D3 netdetect size handling accordingly.

In MVM D3 paths, compute expected payload size as
offsetof(struct iwl_scan_offload_match_info, matches) + matches_len to
preserve previous behavior after the struct layout change.

In MLD D3 netdetect handling, keep the simple full-notification size
assumption and validate against sizeof(*notif) before accessing data.

This keeps scan offload / netdetect functionality unchanged while
making length checks consistent with the new struct definition.

Assisted-by: GitHubCopilot:gpt-5.3-codex
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260715215523.4c4346140bcc.I44313ac41daca352e6aecdba09a1c3570c3eea06@changeid