net: fec: correct the error path for regulator disable in probe

Correct the error path for regulator disable.

Fixes: 9269e556 ("net: fec: add phy-reset-gpios PROBE_DEFER check")
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>