perf trace: Let the perf_evlist__mmap autosize the number of pages to use

So that normal users can run 'trace', we were using a hardcoded 1024
pages value that was more than the default /proc/sys/kernel/perf_event_mlock_kb
setting.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-3banj3yh0sjz41obxtgiel3a@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -2485,7 +2485,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
 			.user_freq     = UINT_MAX,
 			.user_interval = ULLONG_MAX,
 			.no_buffering  = true,
-			.mmap_pages    = 1024,
+			.mmap_pages    = UINT_MAX,
 		},
 		.output = stdout,
 		.show_comm = true,