sched: Remove unnecessary calls to cpufreq_update_util()

The cpufreq update util calls after update_task_ravg() are
no longer needed. This is taken care in WALT when a window is
rolled over. Besides these calls were ineffectual since
SCHED_CPUFREQ_WALT wasn't passed in the flag parameter.

Change-Id: I28ac40b33662584ec9f8fff116e66a6f33a8d010
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>