sched/fair: Rework and comment the group_capacity code
sched/fair: Rework and comment the group_capacity code

Pull out the group_capacity computation so that we can more clearly
comment its issues.

Signed-off-by: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Link: 562ff34f99a00cebec935afff6c2e69f90908fc7@git.kernel.org
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs