perf help: Add missing subcommand `version`

There isn't subcommand `version` when typing `perf help`.

Before :

  $ perf help | grep version
   usage: perf [--version] [--help] [OPTIONS] COMMAND [ARGS]

So add perf-version in command-list.txt for listing it when typing `perf
help`.

After :

$ perf help | grep version

 usage: perf [--version] [--help] [OPTIONS] COMMAND [ARGS]
   version         display the version of perf binary

Signed-off-by: Sangwon Hong <qpakzk@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20180919074911.41931-1-qpakzk@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/command-list.txt

@@ -30,3 +30,4 @@ perf-test			mainporcelain common
 perf-timechart			mainporcelain common
 perf-top			mainporcelain common
 perf-trace			mainporcelain audit
+perf-version			mainporcelain common