perf-annotate doesn't parse perf.data correctly in that it
doesn't read perf header. Fix this by using
mmap_dispatch_perf_file().

Before:

TOTAL events:      17565
      MMAP events:       3221
      LOST events:         10
      COMM events:        235
      EXIT events:          2
  THROTTLE events:          1
UNTHROTTLE events:          2
      FORK events:         10
      READ events:          1
    SAMPLE events:      14083

After:

TOTAL events:      17290
      MMAP events:       3203
      LOST events:          0
      COMM events:        234
      EXIT events:          1
  THROTTLE events:          0
UNTHROTTLE events:          0
      FORK events:          0
      READ events:          0
    SAMPLE events:      13852
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <4B14B201.9030708@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>