resources: allow adjust_resource() for resources with no parent

If a resource has no parent, allow its start/end to be set arbitrarily
as long as any children are still contained within the new range.

[bhelgaas: changelog]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

kernel/resource.c

@@ -722,14 +722,12 @@ int adjust_resource(struct resource *res, resource_size_t start, resource_size_t
 
 	write_lock(&resource_lock);
 
+	if (!parent)
+		goto skip;
+
 	if ((start < parent->start) || (end > parent->end))
 		goto out;
 
-	for (tmp = res->child; tmp; tmp = tmp->sibling) {
-		if ((tmp->start < start) || (tmp->end > end))
-			goto out;
-	}
-
 	if (res->sibling && (res->sibling->start <= end))
 		goto out;
 
@@ -741,6 +739,11 @@ int adjust_resource(struct resource *res, resource_size_t start, resource_size_t
 			goto out;
 	}
 
+skip:
+	for (tmp = res->child; tmp; tmp = tmp->sibling)
+		if ((tmp->start < start) || (tmp->end > end))
+			goto out;
+
 	res->start = start;
 	res->end = end;
 	result = 0;