util/sconfig: emit NULL sibling fields

It's helpful to see the sibling field, even when it's NULL, when
debugging the static.c output from a devictree.cb file. Ensure the
NULL fields are emitted for fullness.

Change-Id: Ib6d5b8164769a6512e762d5a525c7df1f429c866
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39862
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/util/sconfig/main.c b/util/sconfig/main.c
index d784642..b48f992 100644
--- a/util/sconfig/main.c
+++ b/util/sconfig/main.c
@@ -832,6 +832,8 @@
 		fprintf(fil, "\t.link_list = NULL,\n");
 	if (ptr->sibling)
 		fprintf(fil, "\t.sibling = &%s,\n", ptr->sibling->name);
+	else
+		fprintf(fil, "\t.sibling = NULL,\n");
 	fprintf(fil, "#if !DEVTREE_EARLY\n");
 	for (pin = 0; pin < 4; pin++) {
 		if (ptr->pci_irq_info[pin].ioapic_irq_pin > 0)