Merge branch 'net-make-timestamping-selectable'

First part of "net: Make timestamping selectable" from Kory Maincent.
Change the driver-facing type already to lower rebasing pain.

Link: https://lore.kernel.org/20240709-feature_ptp_netnext-v17-0-b5317f50df2a@bootlin.com/


Signed-off-by: Jakub Kicinski <kuba@kernel.org>