Since merging the commit identified in Fixes below, we trigger this
compile time warning:
drivers/md/dm.c: In function ‘__map_bio’:
drivers/md/dm.c:1296:24: warning: unused variable ‘md’ [-Wunused-variable]
 1296 |  struct mapped_device *md = io->md;
       |                        ^~
Remove the 'md' variable.
Fixes: 5a6c35f9af41 ("block: remove direct_make_request")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
        sector_t sector;
        struct bio *clone = &tio->clone;
        struct dm_io *io = tio->io;
-       struct mapped_device *md = io->md;
        struct dm_target *ti = tio->ti;
        blk_qc_t ret = BLK_QC_T_NONE;