thunderbolt: Hide switch attributes that are not set

Thunderbolt host routers may not always contain DROM that includes
device identification information. This is mostly needed for Ice Lake
systems but some Falcon Ridge controllers on PCs also do not have DROM.

In that case hide the identification attributes.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Yehezkel Bernat <YehezkelShB@gmail.com>
Tested-by: Mario Limonciello <mario.limonciello@dell.com>

drivers/thunderbolt/switch.c

@@ -1337,7 +1337,19 @@ static umode_t switch_attr_is_visible(struct kobject *kobj,
 	struct device *dev = container_of(kobj, struct device, kobj);
 	struct tb_switch *sw = tb_to_switch(dev);
 
-	if (attr == &dev_attr_key.attr) {
+	if (attr == &dev_attr_device.attr) {
+		if (!sw->device)
+			return 0;
+	} else if (attr == &dev_attr_device_name.attr) {
+		if (!sw->device_name)
+			return 0;
+	} else if (attr == &dev_attr_vendor.attr)  {
+		if (!sw->vendor)
+			return 0;
+	} else if (attr == &dev_attr_vendor_name.attr)  {
+		if (!sw->vendor_name)
+			return 0;
+	} else if (attr == &dev_attr_key.attr) {
 		if (tb_route(sw) &&
 		    sw->tb->security_level == TB_SECURITY_SECURE &&
 		    sw->security_level == TB_SECURITY_SECURE)