target: Use correct preempted registration sense code

The comments quote the right parts of the spec:

   * d) Establish a unit attention condition for the
   *    initiator port associated with every I_T nexus
   *    that lost its registration other than the I_T
   *    nexus on which the PERSISTENT RESERVE OUT command
   *    was received, with the additional sense code set
   *    to REGISTRATIONS PREEMPTED.

and

   * e) Establish a unit attention condition for the initiator
   *    port associated with every I_T nexus that lost its
   *    persistent reservation and/or registration, with the
   *    additional sense code set to REGISTRATIONS PREEMPTED;

but the actual code accidentally uses ASCQ_2AH_RESERVATIONS_PREEMPTED
instead of ASCQ_2AH_REGISTRATIONS_PREEMPTED.  Fix this.
Signed-off-by: Marco Sanvido <marco@purestorage.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_pr.c

@@ -3120,7 +3120,7 @@ static int core_scsi3_pro_preempt(
 			if (!calling_it_nexus)
 				core_scsi3_ua_allocate(pr_reg_nacl,
 					pr_res_mapped_lun, 0x2A,
-					ASCQ_2AH_RESERVATIONS_PREEMPTED);
+					ASCQ_2AH_REGISTRATIONS_PREEMPTED);
 		}
 		spin_unlock(&pr_tmpl->registration_lock);
 		/*
@@ -3233,7 +3233,7 @@ static int core_scsi3_pro_preempt(
 		 *    additional sense code set to REGISTRATIONS PREEMPTED;
 		 */
 		core_scsi3_ua_allocate(pr_reg_nacl, pr_res_mapped_lun, 0x2A,
-				ASCQ_2AH_RESERVATIONS_PREEMPTED);
+				ASCQ_2AH_REGISTRATIONS_PREEMPTED);
 	}
 	spin_unlock(&pr_tmpl->registration_lock);
 	/*