perf stat: Document --detailed option

perf stat: Document --detailed option

I'm surprised this remained undocumented since at least 2011. And it is
actually a very useful switch, as Steve and I came to realize recently.

Add the text from

  2cba3ffb9a9d ("perf stat: Add -d -d and -d -d -d options to show more CPU events")

which added the incrementing aspect to -d.

Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Davidlohr Bueso <dbueso@suse.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mel Gorman <mgorman@suse.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2cba3ffb9a9d ("perf stat: Add -d -d and -d -d -d options to show more CPU events")
Link: http://lkml.kernel.org/r/1457347294-32546-1-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>