cpufreq: interactive: eliminate dead band effect in low load

the old frequency calculation algorithm that calculates frequency directly proportional to load will result in a dead band effect in low load. at loads near 0, the new frequency calculated is always below min freq, thus causing the min freq to be selected every time. this new algorithm will select the frequencies linearly, such that the min load will result in min freq and so on.

Change-Id: Icd6193f2517542384049c3e6211dc71fc23b60c0
Signed-off-by: Zhao Wei Liew <zhaoweiliew@gmail.com>