Provide PMU event attributes for supported counters and export their symbolic
names to the sysfs "events" directory.

See the /sys/devices/cpum_cf/events/ directory for a list of available counters.
Note that you might require counter set authorizations for the LPAR to use them.
Signed-off-by: NHendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>