net: lan969x: add PTP handler function

Add PTP IRQ handler for lan969x. This is required, as the PTP registers
are placed in two different targets on Sparx5 and lan969x. The
implementation is otherwise the same as on Sparx5.

Also, expose sparx5_get_hwtimestamp() for use by lan969x.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20241024-sparx5-lan969x-switch-driver-2-v2-10-a0b5fae88a0f@microchip.com


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