sched: fix bug in auto adjustment of group upmigrate/downmigrate

sched_group_upmigrate tunable can accept values greater than
100%. Don't limit it to 100% while doing the auto adjustment.

Change-Id: I3d1c1e84f2f4dec688235feb1536b9261a3e808b
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>