target: fix buffer offset in core_scsi3_pri_read_full_status

commit c58a252b upstream.

When at least two initiators register pr on the same LUN,
the target returns the exception data due to buffer offset
error, therefore the initiator executes command 'sg_persist -s'
may cause the initiator to appear segfault error.

This fixes a regression originally introduced by:

  commit a85d667e
  Author: Bart Van Assche <bart.vanassche@sandisk.com>
  Date:   Tue May 23 16:48:27 2017 -0700

      target: Use {get,put}_unaligned_be*() instead of open coding these functions

Signed-off-by: tangwenji <tang.wenji@zte.com.cn>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>