tools/lib/lockdep: Add empty nmi.h

Required since:

  88f1c87 ("locking/lockdep: Avoid triggering hardlockup from debug_show_all_locks()")

Signed-off-by: Sasha Levin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Sasha Levin