bus: ti-sysc: Support modules without control registers

Some modules like MPU have a powerdomain and functional clock but not
necessarily any control registers. Let's allow configuring interconnect
target modules with no control registers.
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/bus/ti-sysc.c

@@ -853,8 +853,12 @@ static int sysc_ioremap(struct sysc *ddata)
  */
 static int sysc_map_and_check_registers(struct sysc *ddata)
 {
+	struct device_node *np = ddata->dev->of_node;
 	int error;
 
+	if (!of_get_property(np, "reg", NULL))
+		return 0;
+
 	error = sysc_parse_and_check_child_range(ddata);
 	if (error)
 		return error;
@@ -2911,6 +2915,9 @@ static int sysc_probe(struct platform_device *pdev)
 	if (!ddata)
 		return -ENOMEM;
 
+	ddata->offsets[SYSC_REVISION] = -ENODEV;
+	ddata->offsets[SYSC_SYSCONFIG] = -ENODEV;
+	ddata->offsets[SYSC_SYSSTATUS] = -ENODEV;
 	ddata->dev = &pdev->dev;
 	platform_set_drvdata(pdev, ddata);