thermal: brcmstb_thermal: Register different ops per process

Since we do not have interrupts on BCM7216, we cannot have trip point
crossing, the thermal subsystem expects us to provide a NULL set_trips
operation in that case, so make it possible to provide per-process
thermal_zone_of_device_ops

Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200114190607.29339-7-f.fainelli@gmail.com