ANDROID: GKI: sched: add rvh for new cfs task util

A vendor hook is added in post_init_entity_util_avg before
a new cfs task's util is attached to cfs_rq's util so that
vendors can gather and modify se's information to modify
scheduling behavior and DVFS as they want.

trace_android_rvh_new_task_stats is not a proper hook because
it is called after the task's util is attached to cfs_rq's util,
which means updating cfs_rq's sched_avg and DVFS request are done.

Bug: 184219858

Signed-off-by: Choonghoon Park <choong.park@samsung.com>
Change-Id: I2deaa93297f8464895978496c9838cdffaa35b7f