sched: Refine the code in unthrottle_cfs_rq()

Directly use rq to save some code.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51AD87EB.1070605@linux.vnet.ibm.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>