ANDROID: sched: Calculate energy consumption of sched_group

For energy-aware load-balancing decisions it is necessary to know the
energy consumption estimates of groups of cpus. This patch introduces a
basic function, sched_group_energy(), which estimates the energy
consumption of the cpus in the group and any resources shared by the
members of the group.

NOTE: The function has five levels of identation and breaks the 80
character limit. Refactoring is necessary.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Change-Id: I0da68f5aef23247db2652fad86ee06749c7e284a
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Git-commit: 3ae1b070
Git-repo: https://android.googlesource.com/kernel/common/


[satyap@codeaurora.org: fix below warning in kernel/sched/fair.c
kernel/sched/fair.c:5429:34: warning: duplicate 'const' \
declaration specifier [-Wduplicate-decl-specifier]]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>