intelli-thermal: use its own dedicated workqueue

this should reduce the load on the shared global workqueue for other
processes and also give its own unique variable name for cpu limit

Signed-off-by: Paul Reioux <reioux@gmail.com>
intelli-thermal: increase sampling time to reduce sampling overhead

Signed-off-by: Paul Reioux <reioux@gmail.com>
Intelli-thermal: remove duplicate header include

Thanks to code review by @Androguide