xfs: split tracepoint classes for deferred items

xfs: split tracepoint classes for deferred items

We're about to start adding support for deferred log intent items for
realtime extents, so split these four types into separate classes so
that we can customize them as the transition happens.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>