phy: lantiq: vrx200-pcie: fix error return code in ltq_vrx200_pcie_phy_power_on()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: e52a6321

 ("phy: lantiq: vrx200-pcie: add a driver for the Lantiq VRX200 PCIe PHY")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>