sched/fair: Always update CPU capacity when load balancing

Limiting CPU capacity updates, which are quite cheap, results in worse
balancing decisions during opportunistic balancing (e.g., SD_BALANCE_WAKE).
This causes opportunistic placement decisions to be skewed using stale CPU
capacity data, and when a CPU isn't idling much, its capacity suffers from
even more staleness since the only exception to the 100 ms capacity update
ratelimit is a CPU exiting idle.

Since the capacity updates are cheap, always do it when load balancing in
order to improve opportunistic task placement decisions.

Change-Id: If1d451ce742fd093010057e31e71012d47fad70a
Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>