sched: Move upmigrate and downmigrate tunables out of SCHED_DEBUG

sched_upmigrate and sched_downmigrate tunables are used
in end user builds. So move these tunable out of SCHED_DEBUG.

Change-Id: I14b5a5e40f367bd0754ec96888e4c63389c67bd0
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[satyap@codeaurora.org: trivial merge conflict resolution]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>