sched: EAS: improve task packing algorithm to avoid excessive packing

Excessive task packing can cause wake up latency more than subtle so
that spoils its purpose.  Also role of WALT's cumulative window demand
is projecting CPU's frequency in the future based on behaviour in the
past which can be varying.  Consequently current task packing algorithm
time to time causes frequency increases which could have been avoided
if scheduler didn't pack begin with.

Improve task packing algorithm to be less aggressive by doing task
packing when there is at least one other CPU is driving CPU's
current frequency or when it's projected packing won't prevent CPU
from dropping frequency.

Change-Id: I9e481549d7698ae999d6abf1e377371bf6e8ab3b
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>