scsi: pm8001: Fix Use plain integer as NULL pointer

Replace assignment of 0 to pointer with NULL assignment.

Link: https://lore.kernel.org/r/20191025135010.GA6191@saurav


Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Acked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>