perf kwork: Add the supported subcommands to the document

Add missing report, latency and timehist subcommands to the document.

Fixes: f98919ec ("perf kwork: Implement 'report' subcommand")
Fixes: ad3d9f7a ("perf kwork: Implement perf kwork latency")
Fixes: bcc8b3e8 ("perf kwork: Implement perf kwork timehist")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Link: https://lore.kernel.org/r/20230812084917.169338-3-yangjihong1@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-kwork.txt

@@ -8,7 +8,7 @@ perf-kwork - Tool to trace/measure kernel work properties (latencies)
 SYNOPSIS
 --------
 [verse]
-'perf kwork' {record}
+'perf kwork' {record|report|latency|timehist}
 
 DESCRIPTION
 -----------