Revert "sched/sysctl: check for min/max values for sched_{up,down}_migrate knobs"

An issue is introduced by 'commit a8ce96ad ("sched/sysctl: check
for min/max values for sched_{up,down}_migrate knobs")' where code ends up
checking always first value of the sched_{up,down}_migrate knobs instead
of checking each value separately in case of multi cluster systems with
more than 2 clusters. This leads to an unexpected behavior as user would
see old values instead of new values like below.

	# cat /proc/sys/kernel/sched_upmigrate
	60 60
	# cat /proc/sys/kernel/sched_downmigrate
	40 40
	# echo "60 95" > /proc/sys/kernel/sched_upmigrate
	# cat /proc/sys/kernel/sched_upmigrate
	60 95
	# echo "40 85" > /proc/sys/kernel/sched_downmigrate
	# cat /proc/sys/kernel/sched_downmigrate
	40 40

The issue that 'commit a8ce96ad ("sched/sysctl: check
for min/max values for sched_{up,down}_migrate knobs")' tried to
resolve is also fixed by 'commit 957cc168 ("sched: restore
all values for sched_{up,down}_migrate knobs in error case")'.
Hence, revert 'commit a8ce96ad ("sched/sysctl: check
for min/max values for sched_{up,down}_migrate knobs")' which
isn't even needed now.

Change-Id: Iec0d569c5c1ee95a04bf77726c1c459b92abd9af
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>