scsi: sd_zbc: Remove an assignment from sd_zbc_setup_report_cmnd()

Since nr_bytes == blk_rq_bytes(rq) == rq->__data_len, the
rq->__data_len = nr_bytes assignment does not modify the value of
rq->__data_len. Hence remove that assignment. Note: the code in
sd_done() that sets the residual to zero for zone report requests
is not affected by this patch.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>