thermal/core: Remove notify ops

With the removal of the notifys user in a previous patches, the ops is no
longer needed, remove it.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lore.kernel.org/r/20201210121514.25760-5-daniel.lezcano@linaro.org