kill DECLARE_MUTEX_LOCKED

DECLARE_MUTEX_LOCKED was used for semaphores used as completions and we've
got rid of them.  Well, except for one in libusual that the maintainer
explicitly wants to keep as semaphore.  So convert that useage to an
explicit sema_init and kill of DECLARE_MUTEX_LOCKED so that new code is
reminded to use a completion.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: "Satyam Sharma" <satyam.sharma@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>