perf tools: Introduce parse_events_terms__purge()

Purges 'struct parse_event_term' entries from a list_head.

Some users need this because they don't allocate space for the list
head, it maybe on the stack or embedded into some other struct.

Next patch will convert users that need just purging and then the
perf_events__free_terms() routine will free the list head as well,
finally being renamed to perf_events_terms__delete().

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: He Kuang <hekuang@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/n/tip-4w3zl4ifcl0ed0j4bu3tckqp@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-events.c

@@ -2068,7 +2068,7 @@ int parse_events_term__clone(struct parse_events_term **new,
 			term->err_term, term->err_val);
 }
 
-void parse_events__free_terms(struct list_head *terms)
+void parse_events_terms__purge(struct list_head *terms)
 {
 	struct parse_events_term *term, *h;
 
@@ -2078,6 +2078,11 @@ void parse_events__free_terms(struct list_head *terms)
 	}
 }
 
+void parse_events__free_terms(struct list_head *terms)
+{
+	parse_events_terms__purge(terms);
+}
+
 void parse_events_evlist_error(struct parse_events_evlist *data,
 			       int idx, const char *str)
 {

tools/perf/util/parse-events.h

@@ -116,6 +116,7 @@ int parse_events_term__sym_hw(struct parse_events_term **term,
 int parse_events_term__clone(struct parse_events_term **new,
 			     struct parse_events_term *term);
 void parse_events__free_terms(struct list_head *terms);
+void parse_events_terms__purge(struct list_head *terms);
 int parse_events__modifier_event(struct list_head *list, char *str, bool add);
 int parse_events__modifier_group(struct list_head *list, char *event_mod);
 int parse_events_name(struct list_head *list, char *name);