perf: Separate find_get_context() from event initialization

perf: Separate find_get_context() from event initialization

Separate find_get_context() from the event allocation and
initialization so that we may make find_get_context() depend
on the event pmu in a later patch.

Signed-off-by: Peter Zijlstra <[email protected]>
Cc: paulus <[email protected]>
Cc: stephane eranian <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Lin Ming <[email protected]>
Cc: Yanmin <[email protected]>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <[email protected]>