scsi: snic: Fix possible UAF in snic_tgt_create()

In the Linux kernel, the following vulnerability has been resolved:

scsi: snic: Fix possible UAF in snic_tgt_create()

Smatch reports a warning as follows:

drivers/scsi/snic/snic_disc.c:307 snic_tgt_create() warn:

'&tgt->list' not removed from list

If device_add() fails in snic_tgt_create(), tgt will be freed, but

tgt->list will not be removed from snic->disc.tgt_list, then list traversal

may cause UAF.

Remove from snic->disc.tgt_list before free().