sched/rt: Add snapshot of changes to RT class

This snapshot is taken from msm-4.19 as of commit 8a6c9078311bc31
("sched: rt: Fix start cpu for RT energy aware task placement").

Change-Id: I850161a6fa845c9a73c67072299476eb3c3d1888
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>