soc: rockchip: io-domain: Fix error return code in rockchip_iodomain_probe()

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

Fixes: e943c43b32 ("PM: AVS: rockchip-io: Move the driver to the rockchip specific drivers")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Link: https://lore.kernel.org/r/1607070805-33038-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/soc/rockchip/io-domain.c

@@ -544,6 +544,7 @@ static int rockchip_iodomain_probe(struct platform_device *pdev)
 		if (uV < 0) {
 			dev_err(iod->dev, "Can't determine voltage: %s\n",
 				supply_name);
+			ret = uV;
 			goto unreg_notify;
 		}