Add new package: cpuload

cpuload is a simple tool to obtain intuitive vision of CPU load
(including total, user, system, irq and softirq) within a certain
time, which is especially useful for embedded system without GUI.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>