thermal/of: Use thermal trips stored in the thermal zone

Now that we have the thermal trip stored in the thermal zone in a
generic way, we can rely on them and remove one indirection we found
in the thermal_of code and do one more step forward the removal of the
duplicated structures.

Cc: Alexandre Bailon <abailon@baylibre.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linexp.org>
Link: https://lore.kernel.org/r/20220722200007.1839356-10-daniel.lezcano@linexp.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>