msm_mpdecision: adjust the hotplug/unplug time thresholds relative to
workqueue delay.

ensure the second core hotplugs ASAP by reducing the hotplug threshold
(90) below workqueue delay (100). msm_mpdecision will have the chance
to bring the second core at every cycle of workqueue. delay unplugging
second core by increasing the unplug threshold (450) above workqueue
delay (100). msm_mpdecision will wait at least five workqueue cycles
before unplugging the extra core after the load decreases to avoid
excessive hotplug events.