scsi: core: add scsi_io_completion_reprep helper

Since the action "reprep" is called from two places, rather than repeat the
code, make a new scsi_io_completion helper with "reprep" as its suffix.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>