perf.data documentation: Clarify HEADER_SAMPLE_TOPOLOGY format

The perf.data file format documentation for HEADER_SAMPLE_TOPOLOGY
specifies the layout in a confusing manner that doesn't match the rest
of the document.  This patch attempts to describe things consistent with
the rest of the file.

Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Chong Jiang <chongjiang@chromium.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Simon Que <sque@chromium.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1908011425240.14303@macbook-air


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