perf: Remove the "event" callback from perf events

As it is not used anymore and has been superseded by overflow_handler.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>

include/linux/perf_event.h

@@ -567,7 +567,6 @@ struct perf_pending_entry {
 
 struct perf_sample_data;
 
-typedef void (*perf_callback_t)(struct perf_event *, void *);
 typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
 					struct perf_sample_data *,
 					struct pt_regs *regs);
@@ -669,8 +668,6 @@ struct perf_event {
 	struct event_filter		*filter;
 #endif
 
-	perf_callback_t			callback;
-
 #endif /* CONFIG_PERF_EVENTS */
 };