perf tools: Remove junk code in mmap size handling

size is overriden later and used only then. Those
lines are only junk, probably a leftover.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>

tools/perf/util/session.c

@@ -1018,9 +1018,6 @@ more:
 
 	if (session->header.needs_swap)
 		perf_event_header__bswap(&event->header);
-	size = event->header.size;
-	if (size == 0)
-		size = 8;
 
 	if (head + event->header.size > mmap_size) {
 		if (mmaps[map_idx]) {