s390/cpum_cf: Add new extended counters for IBM z15

Add CPU measurement counter facility event description for IBM z15.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>