perf vendor events s390: Use s390 machine name instead of type 8561

In the pmu-events directory for JSON file definitions use the
official machine name IBM z15 instead of machine type number
8561. This is consistent with previous machines.
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20190927081147.18345-2-tmricht@linux.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/arch/s390/mapfile.csv

@@ -4,4 +4,4 @@ Family-model,Version,Filename,EventType
 ^IBM.282[78].*[13]\.[1-5].[[:xdigit:]]+$,1,cf_zec12,core
 ^IBM.296[45].*[13]\.[1-5].[[:xdigit:]]+$,1,cf_z13,core
 ^IBM.390[67].*[13]\.[1-5].[[:xdigit:]]+$,3,cf_z14,core
-^IBM.856[12].*3\.6.[[:xdigit:]]+$,3,cf_m8561,core
+^IBM.856[12].*3\.6.[[:xdigit:]]+$,3,cf_z15,core