Power-efficient workqueues

So, this isn't really about audio as such. Audio was chosen as it puts very low load on the CPU and so most of the CPUs should be idle all the time. In general, most of the cases should get benefited from the power efficient workqueues, especially where CPU load is light. The idea is also not to choose a quiesced CPU, but choosing a CPU intelligently (which will improve going down the line with the scheduler becoming more energy aware). Right now it chooses the idlest CPU with the highest level of cache.