s390/cpum_cf: rename IBM z13/z14 counter names

Change the IBM z13/z14 counter names to be in sync with all other models.

Cc: stable@vger.kernel.org # v4.12+
Fixes: 3593eb94 ("s390/cpum_cf: add hardware counter support for IBM z14")
Fixes: 3fc7aceb ("s390/cpum_cf: add IBM z13 counter event names")
Signed-off-by: André Wild <wild@linux.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>