cpuidle: lpm-levels: Use static residency values

Current residency values are calculated based on LPM
parameters such as time overhead, energy overhead, steady
state power and latency. Most of these are unused after
calculating residency.

Remove residency calculation and unused LPM parameters.
Add minimum residency parameter to be used by LPM driver.

Change-Id: I1fc8321bf2ef0454d59c148849a810fb1ecae99c
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>