sched: Add snapshot of Window Assisted Load Tracking (WALT)

This snapshot is taken from msm-4.19 as of commit 5debecbe7195
("trace: filter out spurious preemption and IRQs disable traces").

Change-Id: I8fab4084971baadcaa037f40ab549fc073a4b1ea
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>