ptp: ocp: add shutdown callback

ptp: ocp: add shutdown callback

The shutdown callback was never implemented for this driver, but it's
needed because .remove() callback is never called during kexec/reboot
process. That leaves HW with some interrupts enabled and may cause
spurious interrupt while booting into a new kernel during with kexec.
If it happens that I2C interrupt fires during kexec, the whole I2C bus
is disabled leaving TimeCard with no devlink communication. The same
happens if timestampers were enabled, leaving the card without
timestamper interrupts until full reboot cycle.

Implement .shutdown() callback with the same function as remove
callback.

Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20260611190333.787132-1-vadim.fedorenko@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>