Correct target hiearchy in axone system xml

Previously the comment at the top of this xml file stated that a
MCC has 4 OMIs when in reality it only has 2.

Change-Id: I442beceefcec5ad3601d7b2ec96f89ab52096b46
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/89268
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Reviewed-by: Matt Derksen <mderkse1@us.ibm.com>
Reviewed-by: Ilya Smirnov <ismirno@us.ibm.com>
Reviewed-by: Daniel M Crowell <dcrowell@us.ibm.com>

src/usr/targeting/common/xmltohb/simics_AXONE.system.xml

@@ -5,7 +5,7 @@
 <!--                                                                        -->
 <!-- OpenPOWER HostBoot Project                                             -->
 <!--                                                                        -->
-<!-- Contributors Listed Below - COPYRIGHT 2018,2019                        -->
+<!-- Contributors Listed Below - COPYRIGHT 2018,2020                        -->
 <!-- [+] International Business Machines Corp.                              -->
 <!--                                                                        -->
 <!--                                                                        -->
@@ -38,7 +38,7 @@
      * Each Axone has has 2 MC units
      *     Each MC unit has 2 MI units (a total of 4 per chip)
      *         Each MI unit has 2 MCC units (a total of 8 per chip)
-     *         Each MCC unit has 4 OMI Units (A total of 16 per chip)
+     *         Each MCC unit has 2 OMI Units (A total of 16 per chip)
      *           OMI Units are special as they have two parents (MI + OMIC (more description below))
      *           Each OMI unit connects to 1 OCMB chip
      *             Each OCMB unit contains 1 MEM_PORT unit