thermal/core: Use precomputed jiffies for the polling

The delays are also stored in jiffies based unit. Use them instead of
the ms.

Cc: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org>
Link: https://lore.kernel.org/r/20201216220337.839878-2-daniel.lezcano@linaro.org