Revert "sched: add scheduling latency tracking procfs node"

This reverts commit 692a5361 ("sched: add scheduling latency
tracking procfs node") as this feature is no longer used.

Change-Id: I876eb9b63bc8d8e410a616659b52ab9dbddfca7e
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>