Andi reported problems when parse errors were detected with vendor
events (json), because in the yyparse/parse_events_parse function we
dereferenced the _data parameter to two different structs, with
different layouts, which ended up making parse_events_evlist->error to
point to random stack addresses.

Fix it by making _data to always be struct parse_events_state, changing
the only place where 'struct parse_events_term' was used in
parse_events.y.
Reported-by: Andi Kleen <ak@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-bc27lshz823hxl8n9nkelcgh@git.kernel.org
Fixes: 90e2b22d ("perf/tool: Add support to reuse event grammar to parse out terms")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>