thermal: rockchip: support the sleep pinctrl state to avoid glitches in s2r

When we come out of system suspend state (S3) the tsadc will have been
reset and back at its default state.  While reprogramming the tsadc
it's possible that we'll glitch the output and unintentionally cause
the "over temperature" GPIO to be asserted.  Since the over
temperature GPIO is often hooked up to something that will cause a
reboot or shutdown in hardware, this glitch can be catastrophic on
some boards.

We'll add support for selecting the "sleep" pinctrl state at suspend
time.  Boards can use this to effectively disable the tsadc at suspend
time and avoid glitches when the system is resumed.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>