[SCSI] pm80xx: Fixed return value issue

pm80xx_get_gsm_dump() was returning "1" in error case
instead of negative error value.

Signed-off-by: Viswas G <Viswas.G@pmcs.com>
Reviewed-by: Jack Wang <jinpu.wang@profitbricks.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>