Revert "sched/cputime: Fix steal time accounting vs. CPU hotplug"

This reverts commit 2a8225ef
("sched/cputime: Fix steal time accounting vs. CPU hotplug").

The commit introduces a bug in scheduler book-keeping whereby if a CPU
is hotplugged out for a small duration of time, subsequent time spent
executing tasks gets mis-attributed to interrupts. This in turn results
in unfair scheduling whereby a task can keep executing for a very long
time without any update to it's vruntime. This revert has no side
effects for msm based systems.

Change-Id: Ibb506824c4223551bceb449594ac99f9dfd8064b
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>