ptp: vmclock: Clean up miscdev and ptp clock through devres

Most resources owned by the vmclock device are managed through devres.
Only the miscdev and ptp clock are managed manually.
This makes the code slightly harder to understand than necessary.

Switch them over to devres and remove the now unnecessary drvdata.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>