[SCSI] ipr: Avoid target_destroy accessing memory after it was freed

Defined target_ids,array_ids and vsets_ids as unsigned long to avoid
target_destroy accessing memory after it was freed.

Signed-off-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>