[PATCH] mutex subsystem, semaphore to mutex: XFS

This patch switches XFS over to use the new mutex code directly as
opposed to the previous workaround patch I posted earlier that avoided
the namespace clash by forcing it back to semaphores. This falls in the
'works for me<tm>' category.

Signed-off-by: Jes Sorensen <jes@trained-monkey.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>