s390/pai_crypto: Rename some function for common usage.

s390/pai_crypto: Rename some function for common usage.

To support one common PAI PMU device driver which handles
both PMUs pai_crypto and pai_ext, use a common naming scheme
for structures and variables suitable for both device drivers.
Rename functions
 - paicrypt_free() -> pai_free()
 - paicrypt_destroy_event() -> pai_destroy_event()
 - paicrypt_destroy_event_cpu() -> pai_destroy_event_cpu()
to reflect their future common usage.
No functional change.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Jan Polensky <japo@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>