[SCSI] libosd: check for kzalloc() failure

There wasn't any error handling for this kzalloc().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>