pci: layerscape: Adjust the return value when ls_pcie_addr_valid() fails

When trying to access non-existent/unsupported PCI devices in
ls_pcie_read_config(), when ls_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.
Signed-off-by: NBin Meng <bmeng.cn@gmail.com>

drivers/pci/pcie_layerscape.c

@@ -314,7 +314,7 @@ static int ls_pcie_read_config(struct pci_controller *hose, pci_dev_t d,
 
 	if (ls_pcie_addr_valid(hose, d)) {
 		*val = 0xffffffff;
-		return -EINVAL;
+		return 0;
 	}
 
 	if (PCI_BUS(d) == hose->first_busno) {