soc: qcom: Add a msm_performance module

Sometimes for power saving reasons we might want to keep fewer CPUs
online without adversely affecting performance for certain real world
usecases. This module helps to provide that hotplug support to the
userspace such that it tries to make a best effort in keeping a certain
number of CPUs online as specified by the userspace.
It allows any userspace entity to specify the CPUs that it wants to
manage with this module and of those, the number of CPUs that should be
kept online.

Change-Id: I82c6d6e998d3740ad6f8c67b47344ce87f328b8b
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>