net: ethernet: renesas: rcar_gen4_ptp: Hide private data from users

net: ethernet: renesas: rcar_gen4_ptp: Hide private data from users

The Gen4 PTP helper module is already used by RTSN and RSWITCH to
support PTP clocks and will be used by RAVB too. Hide the Gen4 PTP
private data structure to make sure none of the users poke at it.

This will be more important for RAVB use-cases as more then one RAVB
device will need to cooperate using one PTP clock source.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://patch.msgid.link/20260201183745.1075399-5-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Jakub Kicinski <kuba@kernel.org>