mt76: mt7915: fix hwmon temp sensor mem use-after-free

Without this change, garbage is seen in the hwmon name and sensors output
for mt7915 is garbled. It appears that the hwmon logic does not make a
copy of the incoming string, but instead just copies a char* and expects
it to never go away.

Fixes: 33fe9c6 ("mt76: mt7915: add thermal sensor device support")
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/init.c

@@ -160,9 +160,12 @@ static int mt7915_thermal_init(struct mt7915_phy *phy)
 	struct wiphy *wiphy = phy->mt76->hw->wiphy;
 	struct thermal_cooling_device *cdev;
 	struct device *hwmon;
+	const char *name;
 
-	cdev = thermal_cooling_device_register(wiphy_name(wiphy), phy,
-					       &mt7915_thermal_ops);
+	name = devm_kasprintf(&wiphy->dev, GFP_KERNEL, "mt7915_%s",
+			      wiphy_name(wiphy));
+
+	cdev = thermal_cooling_device_register(name, phy, &mt7915_thermal_ops);
 	if (!IS_ERR(cdev)) {
 		if (sysfs_create_link(&wiphy->dev.kobj, &cdev->device.kobj,
 				      "cooling_device") < 0)
@@ -174,8 +177,7 @@ static int mt7915_thermal_init(struct mt7915_phy *phy)
 	if (!IS_REACHABLE(CONFIG_HWMON))
 		return 0;
 
-	hwmon = devm_hwmon_device_register_with_groups(&wiphy->dev,
-						       wiphy_name(wiphy), phy,
+	hwmon = devm_hwmon_device_register_with_groups(&wiphy->dev, name, phy,
 						       mt7915_hwmon_groups);
 	if (IS_ERR(hwmon))
 		return PTR_ERR(hwmon);