thermal: core: Remove pointless debug traces

The last temperature and the current temperature are show via a
dev_debug. The line before, those temperature are also traced.

It is pointless to duplicate the traces for the temperatures,
remove the dev_dbg traces.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200331165449.30355-2-daniel.lezcano@linaro.org