ptp: ocp: fix error code in probe()

There is a copy and paste error so this uses a valid pointer instead of
an error pointer.

Fixes: 09eeb3ae ("ptp_ocp: implement DPLL ops")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://lore.kernel.org/r/5c581336-0641-48bd-88f7-51984c3b1f79@moroto.mountain


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