dm: Remove unused declaration and empty definition "dm_zone_map_bio"

dm_zone_map_bio() has beed removed since commit f211268e ("dm: Use
the block layer zone append emulation"), remain the declaration unused in
header files. So, let's remove this unused declaration and empty
definition.
Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

drivers/md/dm.h

@@ -109,7 +109,6 @@ void dm_zone_endio(struct dm_io *io, struct bio *clone);
 int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
 			unsigned int nr_zones, report_zones_cb cb, void *data);
 bool dm_is_zone_write(struct mapped_device *md, struct bio *bio);
-int dm_zone_map_bio(struct dm_target_io *io);
 int dm_zone_get_reset_bitmap(struct mapped_device *md, struct dm_table *t,
 			     sector_t sector, unsigned int nr_zones,
 			     unsigned long *need_reset);
@@ -119,10 +118,6 @@ static inline bool dm_is_zone_write(struct mapped_device *md, struct bio *bio)
 {
 	return false;
 }
-static inline int dm_zone_map_bio(struct dm_target_io *tio)
-{
-	return DM_MAPIO_KILL;
-}
 #endif
 
 /*