perf report: Fix indentation of dynamic entries in hierarchy

When dynamic entries are used in the hierarchy mode with multiple
events, the output might not be aligned properly.  In the hierarchy
mode, the each sort column is indented using total number of sort keys.
So it keeps track of number of sort keys when adding them.  However
a dynamic sort key can be added more than once when multiple events have
same field names.  This results in unnecessarily long indentation in the
output.

For example perf kmem records following events:

  $ perf evlist --trace-fields -i perf.data.kmem
  kmem:kmalloc: trace_fields: call_site,ptr,bytes_req,bytes_alloc,gfp_flags
  kmem:kmalloc_node: trace_fields: call_site,ptr,bytes_req,bytes_alloc,gfp_flags,node
  kmem:kfree: trace_fields: call_site,ptr
  kmem:kmem_cache_alloc: trace_fields: call_site,ptr,bytes_req,bytes_alloc,gfp_flags
  kmem:kmem_cache_alloc_node: trace_fields: call_site,ptr,bytes_req,bytes_alloc,gfp_flags,node
  kmem:kmem_cache_free: trace_fields: call_site,ptr
  kmem:mm_page_alloc: trace_fields: page,order,gfp_flags,migratetype
  kmem:mm_page_free: trace_fields: page,order

As you can see, many field names shared between kmem events.  So adding
'ptr' dynamic sort key alone will set nr_sort_keys to 6.  And this adds
many unnecessary spaces between columns.

Before:

  $ perf report -i perf.data.kmem --hierarchy -s ptr -g none --stdio
  ...
  #                Overhead                 ptr
  # .......................  ...................................
  #
      99.89%                 0xffff8803ffb79720
       0.06%                 0xffff8803d228a000
       0.03%                 0xffff8803f7678f00
       0.00%                 0xffff880401dc5280
       0.00%                 0xffff880406172380
       0.00%                 0xffff8803ffac3a00
       0.00%                 0xffff8803ffac1600

After:

  # Overhead                 ptr
  # ........  ....................
  #
      99.89%  0xffff8803ffb79720
       0.06%  0xffff8803d228a000
       0.03%  0xffff8803f7678f00
       0.00%  0xffff880401dc5280
       0.00%  0xffff880406172380
       0.00%  0xffff8803ffac3a00
       0.00%  0xffff8803ffac1600

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1456512767-1164-2-git-send-email-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>