wifi: mac80211: allow 64-bit radiotap timestamps

When reporting the radiotap timestamp, the mactime field is
usually unused, we take the data from the device_timestamp.
However, there can be cases where the radiotap timestamp is
better reported as a 64-bit value, so since the mactime is
free, add a flag to support using the mactime as a 64-bit
radiotap timestamp.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231220133549.00c8b9234f0c.Ie3ce5eae33cce88fa01178e7aea94661ded1ac24@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>