Revert "perf pmu: Fix pmu events parsing rule"

As reported by Adrian Hunter, this breaks intel_pt event parsing:

# perf record -e intel_pt//u uname
event syntax error: 'intel_pt//u'
\___ parser error
Run 'perf list' for a list of valid events

Usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]

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

This reverts commit 9a4a931ce847f4aaa12edf11b2e050e18bf45910.

Reported-by: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/parse-events.y

···
 	   event_bpf_file
 
 event_pmu:
-PE_NAME '/' event_config '/'
+PE_NAME opt_event_config
 {
 	struct list_head *list, *orig_terms, *terms;
 
-	if (parse_events_copy_term_list($3, &orig_terms))
+	if (parse_events_copy_term_list($2, &orig_terms))
 		YYABORT;
 
 	ALLOC_LIST(list);
-	if (parse_events_add_pmu(_parse_state, list, $1, $3, false)) {
+	if (parse_events_add_pmu(_parse_state, list, $1, $2, false)) {
 		struct perf_pmu *pmu = NULL;
 		int ok = 0;
 		char *pattern;
···
 		if (!ok)
 			YYABORT;
 	}
-	parse_events_terms__delete($3);
+	parse_events_terms__delete($2);
 	parse_events_terms__delete(orig_terms);
 	$$ = list;
 }