ptp: ptp_vmclock: Add device tree support

ptp: ptp_vmclock: Add device tree support

Add device tree support to the ptp_vmclock driver, allowing it to probe
via device tree in addition to ACPI.

Handle optional interrupt for clock disruption notifications, mirroring
the ACPI notification behaviour.

Although the interrupt is marked as 'optional' in the DT bindings, if
the device *advertises* the VMCLOCK_FLAG_NOTIFICATION_ABSENT then it
*should* have an interrupt. The driver will refuse to initialize if not.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Babis Chalios <bchalios@amazon.es>
Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
Tested-by: Takahiro Itazuri <itazur@amazon.com>
Link: https://patch.msgid.link/20260130173704.12575-5-itazur@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>