msm: mpdecision: Add mpdecision driver code

This driver is mainly responsible to convey the runqueue average and
iowait average values to the TZ periodically. The TZ returns the mask
of the cpu's that should be online and the slack timer.

The mpdecision code brings cpus up or down to match the online mask
from TZ. Also starts the slack timer as specified by TZ.

Upon expiry of the slack timer mpdecision calls TZ to get a new
mask and a new slack timer.

Change-Id: I23bb057ffec2630b9fe826da9cbd4edff08d3889
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>