sched: Convert the only user of cond_resched_bkl to use cond_resched()

fs/locks.c:flock_lock_file() is the only user of
cond_resched_bkl()

This helper doesn't do anything more than cond_resched(). The
latter naming is enough to explain that we are rescheduling if
needed.

The bkl suffix suggests another semantics but it's actually a
synonym of cond_resched().

Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1247725694-6082-7-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>