perf parse-events: Fix tracepoint name memory leak

Fuzzing found that an invalid tracepoint name would create a memory
leak with an address sanitizer build:
```
$ perf stat -e '*:o/' true
event syntax error: '*:o/'
                       \___ parser error
Run 'perf list' for a list of valid events

 Usage: perf stat [<options>] [<command>]

    -e, --event <event>   event selector. use 'perf list' to list available events

=================================================================
==59380==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 4 byte(s) in 2 object(s) allocated from:
    #0 0x7f38ac07077b in __interceptor_strdup ../../../../src/libsanitizer/asan/asan_interceptors.cpp:439
    #1 0x55f2f41be73b in str util/parse-events.l:49
    #2 0x55f2f41d08e8 in parse_events_lex util/parse-events.l:338
    #3 0x55f2f41dc3b1 in parse_events_parse util/parse-events-bison.c:1464
    #4 0x55f2f410b8b3 in parse_events__scanner util/parse-events.c:1822
    #5 0x55f2f410d1b9 in __parse_events util/parse-events.c:2094
    #6 0x55f2f410e57f in parse_events_option util/parse-events.c:2279
    #7 0x55f2f4427b56 in get_value tools/lib/subcmd/parse-options.c:251
    #8 0x55f2f4428d98 in parse_short_opt tools/lib/subcmd/parse-options.c:351
    #9 0x55f2f4429d80 in parse_options_step tools/lib/subcmd/parse-options.c:539
    #10 0x55f2f442acb9 in parse_options_subcommand tools/lib/subcmd/parse-options.c:654
    #11 0x55f2f3ec99fc in cmd_stat tools/perf/builtin-stat.c:2501
    #12 0x55f2f4093289 in run_builtin tools/perf/perf.c:322
    #13 0x55f2f40937f5 in handle_internal_command tools/perf/perf.c:375
    torvalds#14 0x55f2f4093bbd in run_argv tools/perf/perf.c:419
    torvalds#15 0x55f2f409412b in main tools/perf/perf.c:535

SUMMARY: AddressSanitizer: 4 byte(s) leaked in 2 allocation(s).
```
Fix by adding the missing destructor.

Fixes: 865582c ("perf tools: Adds the tracepoint name parsing support")
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: He Kuang <hekuang@huawei.com>
Link: https://lore.kernel.org/r/20230914164028.363220-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/util/parse-events.y

@@ -103,6 +103,7 @@ static void free_list_evsel(struct list_head* list_evsel)
 %type <list_evsel> groups
 %destructor { free_list_evsel ($$); } <list_evsel>
 %type <tracepoint_name> tracepoint_name
+%destructor { free ($$.sys); free ($$.event); } <tracepoint_name>
 %type <hardware_term> PE_TERM_HW
 %destructor { free ($$.str); } <hardware_term>