thermal: rockchip: fixes the period time for tsadc

We should increase the period cycles to save power since the rk3399 has
the high frequency for tsadc clock.

Fixes commit b0d70338
("thermal: rockchip: Support the RK3399 SoCs in thermal driver")

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>