perf trace: Pack 'struct trace'

perf trace: Pack 'struct trace'

Initial struct stats:

	/* size: 368, cachelines: 6, members: 24 */
	/* sum members: 353, holes: 3, sum holes: 15 */
	/* last cacheline: 48 bytes */

After reorg:

[acme@ssdandy linux]$ pahole -C trace ~/bin/trace | tail -4
	/* size: 360, cachelines: 6, members: 24 */
	/* padding: 7 */
	/* last cacheline: 40 bytes */
};
[acme@ssdandy linux]$

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.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-6jimc80yu89qkx6zb8465s6t@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>