x86: quark: Initialize thermal sensor properly

Thermal sensor on Quark SoC needs to be properly initialized per
Quark firmware writer guide, otherwise when booting Linux kernel,
it triggers system shutdown because of wrong temperature in the
thermal sensor is detected by the kernel driver (see below):

[    5.119819] thermal_sys: Critical temperature reached(206 C),shutting down
[    5.128997] Failed to start orderly shutdown: forcing the issue
[    5.135495] Emergency Sync complete

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>