s390/pai_crypto: remove per-cpu variable assignement in event initialization

Function paicrypt_event_init() initializes the PMU device driver
specific details for an event. It is called once per event creation.
The function paicrypt_event_init() is not necessarily executed on
that CPU the event will be used for.
When an event is activated, function paicrypt_start() is used to
start the event on that CPU.
The per CPU data structure struct paicrypt_map has a pointer to
the event which is active for a particular CPU. This pointer is
set in function paicrypt_start() to point to the currently installed
event. There is no need to also set this pointer in function
paicrypt_event_init() where is might be assigned to the wrong CPU.
Therefore remove this assignment in paicrypt_event_init().

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