thermal: rockchip: fixes the exception interrupts

The hardware-tracked trips will set the alarm interrupt value for
registers. Then when the thermal zone has no trips to be set,
That make the thermal trips callback a over range value.

The root cause is the rk_tsadcv2_temp_to_code() function to handle the
invalid temperature range is indeed incorrect, let's fix it on now.
Otherwise, the thermal alarm interrupt will be triggered all the time
on some SoCs.

Fox example:
localhost tmp # grep thermal /proc/interrupts; sleep 5;
grep thermal /proc/interrupts

23:     994830  ..    GICv3 129 Level     rockchip_thermal
23:    1003423  ..    GICv3 129 Level     rockchip_thermal

Reported-by: Rocky Hao <rocky.hao@rock-chips.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>