scsi: target: Fix iscsi transport id buffer setup
This fixes the following bugs with the transport id setup for iscsi:
1. Incorrectly adding NULL after initiator name for TPID format 1.
2. For TPID format 1 buffer setup we are doing off+len, off++ and then
also len+=some_value. This results in the isid going past buffer
boundaries when we then do buf[off+len]
3. The pr_reg_isid is the isid in string format which is 12 bytes, but we
are only copying 6 bytes.
Link: https://lore.kernel.org/r/1593654203-12442-6-git-send-email-michael.christie@oracle.com
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>