ARM: dts: ux500: Fix up the CPU thermal zone

This fixes up the default ux500 CPU thermal zone:

- Set polling delay to 0 and explain why
- Set passive polling delay to 250
- Remove restrictions from the CPU cooling device,
  we should use all cpufreq steps to cool down if
  needed.

Link: https://lore.kernel.org/r/20191001074628.8122-1-linus.walleij@linaro.org


Fixes: b786a05f ("ARM: dts: ux500: Update thermal zone")
Suggested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>