sched/rt: Add snapshot of changes to RT class

This snapshot is taken from msm-4.14 as of commit 47b6f627f16cf9d
("Merge android-4.14-p.68 (2c79578) into msm-4.14").

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