Replace the typeless b_fspriv2 and the ugly macros around it with a properly
typed transaction pointer.  As a fallout the log buffer state debug checks
are also removed.  We could have kept them using casts, but as they do
not have a real purpose we can as well just remove them.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAlex Elder <aelder@sgi.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>