thermal: rockchip: fix compile error

Missing a include file caused compile error.

  drivers/thermal/rockchip_thermal.c: In function 'rockchip_thermal_suspend':
  drivers/thermal/rockchip_thermal.c:720:2: error: implicit declaration of function 'pinctrl_pm_select_sleep_state' [-Werror=implicit-function-declaration]
  ...

Fixes: 7e38a5b1

 ("thermal: rockchip: support the sleep pinctrl state
to avoid glitches")

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>