phy: ocelot-serdes: Fix IS_ERR vs NULL bug in serdes_probe()

[Markus Elfring]

> Good find.
>
> Acked-by: colin.foster at in-advantage.com
> Revieved-by: colin.foster at in-advantage.com

Please reconsider the usage of these tags once more.

* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.12-rc5#n456

* Should a personal name be mentioned (besides the email address)?


Regards,
Markus