scsi: scsi_debug: Fix buffer size of REPORT ZONES command

According to ZBC and SPC specifications, the unit of ALLOCATION LENGTH
field of REPORT ZONES command is byte. However, current scsi_debug
implementation handles it as number of zones to calculate buffer size to
report zones. When the ALLOCATION LENGTH has a large number, this results
in too large buffer size and causes memory allocation failure.  Fix the
failure by handling ALLOCATION LENGTH as byte unit.

Link: https://lore.kernel.org/r/20211207010638.124280-1-shinichiro.kawasaki@wdc.com
Fixes: f0d1cf93

 ("scsi: scsi_debug: Add ZBC zone commands")
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>