dm: remove unused _rq_tio_cache and _rq_cache

Also move dm_rq_target_io structure definition from dm-rq.h to dm-rq.c

Fixes: 6a23e05c2fe3c6 ("dm: remove legacy request-based IO path")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
3 files changed