sched/dl: Use dl_bw_of() under rcu_read_lock_sched()

sched/dl: Use dl_bw_of() under rcu_read_lock_sched()

rq->rd is freed using call_rcu_sched(), so rcu_read_lock() to access it
is not enough. We should use either rcu_read_lock_sched() or preempt_disable().

Reported-by: Sasha Levin <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Kirill Tkhai <[email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Fixes: 66339c31bc39 "sched: Use dl_bw_of() under RCU read lock"
Link: http://lkml.kernel.org/r/1412065417.20287.24.camel@tkhai
Signed-off-by: Ingo Molnar <[email protected]>