powerpc/numa: Look for ibm, associativity-reference-points at the root

If we don't find ibm,associativity-reference-points as a child of
/rtas, look for it at the root of the tree instead. We use this on
Book3E where we have no RTAS but still use the sPAPR conventions
for NUMA.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/numa.c

@@ -311,14 +311,13 @@ EXPORT_SYMBOL_GPL(of_node_to_nid);
 static int __init find_min_common_depth(void)
 {
 	int depth;
-	struct device_node *rtas_root;
 	struct device_node *chosen;
+	struct device_node *root;
 	const char *vec5;
 
-	rtas_root = of_find_node_by_path("/rtas");
-
-	if (!rtas_root)
-		return -1;
+	root = of_find_node_by_path("/rtas");
+	if (!root)
+		root = of_find_node_by_path("/");
 
 	/*
 	 * This property is a set of 32-bit integers, each representing
@@ -332,7 +331,7 @@ static int __init find_min_common_depth(void)
 	 * NUMA boundary and the following are progressively less significant
 	 * boundaries. There can be more than one level of NUMA.
 	 */
-	distance_ref_points = of_get_property(rtas_root,
+	distance_ref_points = of_get_property(root,
 					"ibm,associativity-reference-points",
 					&distance_ref_points_depth);
 
@@ -376,11 +375,11 @@ static int __init find_min_common_depth(void)
 		distance_ref_points_depth = MAX_DISTANCE_REF_POINTS;
 	}
 
-	of_node_put(rtas_root);
+	of_node_put(root);
 	return depth;
 
 err:
-	of_node_put(rtas_root);
+	of_node_put(root);
 	return -1;
 }