selftests/powerpc/pmu: Include mmap_buffer field as part of struct event

To enable the capturing of samples as part of perf event, add a new
field "mmap_buffer" to "struct event". This field is a place-holder for
sample collection
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220127072012.662451-2-kjain@linux.ibm.com

tools/testing/selftests/powerpc/pmu/event.h

@@ -22,6 +22,11 @@ struct event {
 		u64 running;
 		u64 enabled;
 	} result;
+	/*
+	 * mmap buffer used while recording sample.
+	 * Accessed as "struct perf_event_mmap_page"
+	 */
+	void *mmap_buffer;
 };
 
 void event_init(struct event *e, u64 config);