perf metricgroup: Constify variables storing the result of strchr() on const tables

commit b428686 upstream.

As newer glibcs will propagate the const attribute of the searched table
to its return.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: acmel

tools/perf/util/metricgroup.c

@@ -364,7 +364,7 @@ static int setup_metric_events(const char *pmu, struct hashmap *ids,
 static bool match_metric_or_groups(const char *metric_or_groups, const char *sought)
 {
 	int len;
-	char *m;
+	const char *m;
 
 	if (!sought)
 		return false;
@@ -439,11 +439,10 @@ static const char *code_characters = ",-=@";
 
 static int encode_metric_id(struct strbuf *sb, const char *x)
 {
-	char *c;
 	int ret = 0;
 
 	for (; *x; x++) {
-		c = strchr(code_characters, *x);
+		const char *c = strchr(code_characters, *x);
 		if (c) {
 			ret = strbuf_addch(sb, '!');
 			if (ret)