perf kvm: Update documentation to reflect new changes

Update documentation for new sorting and option '--stdio'.
Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20230315145112.186603-2-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-kvm.txt

@@ -58,7 +58,7 @@ There are a couple of variants of perf kvm:
   events.
 
   'perf kvm stat report' reports statistical data which includes events
-  handled time, samples, and so on.
+  handled sample, percent_sample, time, percent_time, max_t, min_t, mean_t.
 
   'perf kvm stat live' reports statistical data in a live mode (similar to
   record + report but with statistical data updated live at a given display
@@ -82,6 +82,8 @@ OPTIONS
 :GMEXAMPLESUBCMD: top
 include::guest-files.txt[]
 
+--stdio:: Use the stdio interface.
+
 -v::
 --verbose::
 	Be more verbose (show counter open errors, etc).
@@ -97,7 +99,10 @@ STAT REPORT OPTIONS
 -k::
 --key=<value>::
        Sorting key. Possible values: sample (default, sort by samples
-       number), time (sort by average time).
+       number), percent_sample (sort by sample percentage), time
+       (sort by average time), precent_time (sort by time percentage),
+       max_t (sort by maximum time), min_t (sort by minimum time), mean_t
+       (sort by mean time).
 -p::
 --pid=::
     Analyze events only for given process ID(s) (comma separated list).