thermal: add the note for set_trip_temp

Fixes commit 60f9ce3ada53
("thermal: of-thermal: allow setting trip_temp on hardware")

Signed-off-by: Caesar Wang <[e-mail]>
Cc: Zhang Rui <[e-mail]>
Cc: Eduardo Valentin <[e-mail]>
Cc: [e-mail]
Signed-off-by: Zhang Rui <[e-mail]>

include/linux/thermal.h

···
  * @get_trend: a pointer to a function that reads the sensor temperature trend.
  * @set_emul_temp: a pointer to a function that sets sensor emulated
  *		   temperature.
+ * @set_trip_temp: a pointer to a function that sets the trip temperature on
+ *		   hardware.
  */
 struct thermal_zone_of_device_ops {
 	int (*get_temp)(void *, int *);