drm/etnaviv: constify static struct cooling_ops

The only usage of cooling_ops is to pass its address to
thermal_of_cooling_device_register(), which takes a pointer to const
struct thermal_cooling_device_ops as input. Make it const to allow the
compiler to put it in read-only memory.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

drivers/gpu/drm/etnaviv/etnaviv_gpu.c

@@ -1658,7 +1658,7 @@ etnaviv_gpu_cooling_set_cur_state(struct thermal_cooling_device *cdev,
 	return 0;
 }
 
-static struct thermal_cooling_device_ops cooling_ops = {
+static const struct thermal_cooling_device_ops cooling_ops = {
 	.get_max_state = etnaviv_gpu_cooling_get_max_state,
 	.get_cur_state = etnaviv_gpu_cooling_get_cur_state,
 	.set_cur_state = etnaviv_gpu_cooling_set_cur_state,