thermal: bcm2835: constify thermal_zone_of_device_ops structures

The thermal_zone_of_device_ops structure is only passed as the fourth
argument to thermal_zone_of_sensor_register, which is declared as const.
Thus the thermal_zone_of_device_ops structure itself can be const.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>