dm: fix REQ_OP_ZONE_RESET bio handling

The REQ_OP_ZONE_RESET bio has no payload and zero sectors.  Its position
is the only information used to indicate the zone to reset on the
device.  Due to its zero length, this bio is not cloned and sent to the
target through the non-flush case in __split_and_process_bio().  Add an
additional case in that function to call __split_and_process_non_flush()
without checking the clone info size.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>