pci: imx: Adjust the return value when imx_pcie_addr_valid() fails

When trying to access non-existent/unsupported PCI devices in
imx_pcie_read_config(), when imx_pcie_addr_valid() fails it returns
error code and fills in the result with 0xffffffff manually. But it
really should return zero to upper layer codes.

Reported-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Fabio Estevam <fabio.estevam@nxp.com>

drivers/pci/pcie_imx.c

@@ -381,7 +381,7 @@ static int imx_pcie_read_config(struct pci_controller *hose, pci_dev_t d,
 	ret = imx_pcie_addr_valid(d);
 	if (ret) {
 		*val = 0xffffffff;
-		return ret;
+		return 0;
 	}
 
 	va_address = get_bus_address(d, where);