thermal: rcar_gen3_thermal: Do not use interrupts for normal operation

Remove the usage of interrupts for the normal temperature operation and
depend on the polling performed by the thermal core. This is done to
prepare to use the interrupts as they are intended to trigger once
specific trip points are passed and not to react to temperature changes
in the normal operational range.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201126220923.3107213-1-niklas.soderlund+renesas@ragnatech.se