sync_aiocb is unused since commit ce1a14dc (Dynamically allocate AIO
Completion Blocks., 2006-08-07).

private is unused since commit 56a14938 (drive cleanup fixes., 2009-09-25).
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>