PCI: cpqphp: Fix possible NULL pointer dereference

Check io_node for NULL before dereferencing it.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>

drivers/pci/hotplug/cpqphp_ctrl.c

@@ -2812,18 +2812,16 @@ static int configure_new_function(struct controller *ctrl, struct pci_func *func
 
 					dbg("CND:      length = 0x%x\n", base);
 					io_node = get_io_resource(&(resources->io_head), base);
+					if (!io_node)
+						return -ENOMEM;
 					dbg("Got io_node start = %8.8x, length = %8.8x next (%p)\n",
 					    io_node->base, io_node->length, io_node->next);
 					dbg("func (%p) io_head (%p)\n", func, func->io_head);
 
 					/* allocate the resource to the board */
-					if (io_node) {
 					base = io_node->base;
-
 					io_node->next = func->io_head;
 					func->io_head = io_node;
-					} else
-						return -ENOMEM;
 				} else if ((temp_register & 0x0BL) == 0x08) {
 					/* Map prefetchable memory */
 					base = temp_register & 0xFFFFFFF0;