ANDROID: cpuset: Make cpusets restore on hotplug

This deliberately changes the behavior of the per-cpuset
cpus file to not be effected by hotplug. When a cpu is offlined, it will
be removed from the cpuset/cpus file. When a cpu is onlined, if the cpuset
originally requested that cpu be a part of the cpuset, that cpu will be
restored to the cpuset. The cpus files still have to be hierachical, but
the ranges no longer have to be out of the currently online cpus, just the
physically present cpus.

This reverts commit 3fc3fe75 ("Revert "ANDROID: cpuset: Make cpusets
restore on hotplug""). Reverting the revert effectively bringing back
the original change.

Bug: 174125747
Bug: 120444281
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
[AmitP: Refactored original changes to align with upstream commit
201af4c0 ("cgroup: move cgroup files under kernel/cgroup/")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
[satyap@codeaurora.org: port to android-mainline kernel]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>
[SaiHarshiniN: Resolved merge conflict post 6.1-rc1]
Signed-off-by: Sai Harshini Nimmala <quic_snimmala@quicinc.com>
Change-Id: I588f6172c15b48ecadb85f161dae948ce9aeca93