FIXUP: sched: fix set_cfs_cpu_capacity when WALT is in use

The CPU utilization reported when WALT is in use already tracks the
contributions due to RT and DL workloads. However, SchedFreq exposes
different capacity update functions, one for each class, and does classes
utilization internally at update_cpu_capacity_request() call time.

This patch ensures that when WALT is in use, the:
  cpu_sched_capacity_reqs::cfs
value is tracking just the load generated by SCHED_OTHER tasks.

Change-Id: Ibd9c9a10874a1d91f62477034548f7664e57cd6a
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>