futex: use lockdep_assert_held() for lock checking

futex: use lockdep_assert_held() for lock checking

Use lockdep_assert_held() for lock checking instead of a strange homegrown
variant.  This removes the return for this case, but that is unlikely to
be useful anyway.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>