thermal/core: Fix memory leak in the error path

Fix the following error:

 smatch warnings:
 drivers/thermal/thermal_core.c:1020 __thermal_cooling_device_register() warn: possible memory leak of 'cdev'

by freeing the cdev when exiting the function in the error path.

Fixes: 58483761 ("thermal/drivers/core: Use a char pointer for the cooling device name")
Reported-by: Nkernel test robot <lkp@intel.com>
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210319202257.890848-1-daniel.lezcano@linaro.org

drivers/thermal/thermal_core.c

@@ -1017,6 +1017,7 @@ __thermal_cooling_device_register(struct device_node *np,
 out_ida_remove:
 	ida_simple_remove(&thermal_cdev_ida, cdev->id);
 out_kfree_cdev:
+	kfree(cdev);
 	return ERR_PTR(ret);
 }