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: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/pci/pcie_layerscape.c b/drivers/pci/pcie_layerscape.c
index 58e88ae..99f9c83 100644
--- a/drivers/pci/pcie_layerscape.c
+++ b/drivers/pci/pcie_layerscape.c
@@ -314,7 +314,7 @@
 
 	if (ls_pcie_addr_valid(hose, d)) {
 		*val = 0xffffffff;
-		return -EINVAL;
+		return 0;
 	}
 
 	if (PCI_BUS(d) == hose->first_busno) {