phy: Use PTR_ERR_OR_ZERO to fix warning raised by coccinelle

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: coccinelle/api/ptr_ret.cocci

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>