wifi: cfg80211: expose update timestamp to drivers

This information is exposed to userspace but not drivers. Make this
field public so that drivers are also able to access it. The information
is for example useful for link selection to determine whether the BSS
corresponding to an MLO link has been seen in a recent scan.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250212082137.b682ee7aebc8.I0f7cca9effa2b1cee79f4f2eb8b549c99b4e0571@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>