ANDROID: sched/fair: fix energy compute when a cluster is only a cpu core in multi-cluster system

when a cluster is only a cpu core in multi-cluster system, compute_energy will only
compute cpu core power(MC domain),but the power consumed by the DIE domain is not
computed.

fix the bug,end compute energy in DIE domain.

Bug: 120440300
Change-Id: I9d3ae6eb3dcb384fba164cf6072b85318bdc5e68
Signed-off-by: Samer Xie <samer.xie@unisoc.com>
(cherry picked from commit cfbe30be85c4eb6743fd6eb05dcbf8cb1a3e1d0a
 https://android.googlesource.com/kernel/common

 android-4.14)
(fixed trivial cherry-pick conflict caused by sched_group_span() being
 called sched_group_cpus() in 4.9)
Signed-off-by: Quentin Perret <quentin.perret@arm.com>