sched: Move code around

In preparation to other code movement, move weighted_cpuload(),
source_load() and target_load() before the class includes.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>