thermal/drivers/loongson2: Constify struct thermal_zone_device_ops

'struct thermal_zone_device_ops' could be left unmodified in this driver.

Constifying this structure moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.

This partly reverts commit 734b5def91b5 ("thermal/drivers/loongson2: Add
Loongson-2K2000 support") which removed the const qualifier. Instead,
define two different structures.

On a x86_64, with allmodconfig:
Before:
======
text data bss dec hex filename
5089 1160 0 6249 1869 drivers/thermal/loongson2_thermal.o

After:
=====
text data bss dec hex filename
5464 1128 0 6592 19c0 drivers/thermal/loongson2_thermal.o

Signed-off-by: Christophe JAILLET <[e-mail]>
Link: https://lore.kernel.org/r/5f5f815f85[e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>

drivers/thermal/loongson2_thermal.c

···
 	return loongson2_thermal_set(data, low/MILLI, high/MILLI, true);
 }
 
-static struct thermal_zone_device_ops loongson2_of_thermal_ops = {
+static const struct thermal_zone_device_ops loongson2_2k1000_of_thermal_ops = {
 	.get_temp = loongson2_2k1000_get_temp,
+	.set_trips = loongson2_thermal_set_trips,
+};
+
+static const struct thermal_zone_device_ops loongson2_2k2000_of_thermal_ops = {
+	.get_temp = loongson2_2k2000_get_temp,
 	.set_trips = loongson2_thermal_set_trips,
 };
 
 static int loongson2_thermal_probe(struct platform_device *pdev)
 {
+	const struct thermal_zone_device_ops *thermal_ops;
 	struct device *dev = &pdev->dev;
 	struct loongson2_thermal_data *data;
 	struct thermal_zone_device *tzd;
···
 		if (IS_ERR(data->temp_reg))
 			return PTR_ERR(data->temp_reg);
 
-		loongson2_of_thermal_ops.get_temp = loongson2_2k2000_get_temp;
+		thermal_ops = &loongson2_2k2000_of_thermal_ops;
+	} else {
+		thermal_ops = &loongson2_2k1000_of_thermal_ops;
 	}
 
 	irq = platform_get_irq(pdev, 0);
···
 	loongson2_thermal_set(data, 0, 0, false);
 
 	for (i = 0; i <= LOONGSON2_MAX_SENSOR_SEL_NUM; i++) {
-		tzd = devm_thermal_of_zone_register(dev, i, data,
-						    &loongson2_of_thermal_ops);
+		tzd = devm_thermal_of_zone_register(dev, i, data, thermal_ops);
 
 		if (!IS_ERR(tzd))
 			break;