thermal/drivers/rcar: Remove notification usage

The ops is only showing a trace telling a critical trip point is
crossed. The same information is given by the thermal framework.

This is redundant, remove the code.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20201210121514.25760-4-daniel.lezcano@linaro.org