thermal/drivers/tegra: Remove get_trend function

The get_trend function does already what the generic framework does.

Remove it.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://lore.kernel.org/r/20220616202537.303655-2-daniel.lezcano@linaro.org


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>