thermal: rcar_gen3_thermal: Generate interrupt when temperature changes

The desired behavior of the driver is to generate an interrupt and call
thermal_zone_device_update() as soon as the temperature have changed
more then one degree.

When the set_trips operation was implemented it was believed that the
trip window set by the framework would move around the current
temperature and the hysteresis value described in devicetree. The
behavior of the framework is however to set a window based on the trip
points described in devicetree.

Remove the set_trips operation which was not used correctly and update
the temperatures that triggers interrupts directly from the interrupt
handler.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200212224917.737314-1-niklas.soderlund+renesas@ragnatech.se