ANDROID: sched, trace: Remove trace event sched_load_avg_cpu

The functionality of sched_load_avg_cpu can be provided by
sched_load_cfs_rq.
The WALT extension will be included into sched_load_cfs_rq by patch
(ANDROID: trace: Add WALT util signal to trace event sched_load_cfs_rq).

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Change-Id: I2e3944a6e60a77e3237b7c8cb29cbd840118a6ad