perf metricgroup: Remove needless includes from metricgroup.h

There we need just some struct forward declarations, do that instead and
add the includes needed by metricgroup.c.

That should help with needless rebuilds when changing the removed
headers from metricgroup.h.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-1fkskjws6imir2hhztqhdyb0@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/metricgroup.c

@@ -7,18 +7,19 @@
 
 #include "metricgroup.h"
 #include "evlist.h"
+#include "evsel.h"
 #include "strbuf.h"
 #include "pmu.h"
 #include "expr.h"
 #include "rblist.h"
 #include <string.h>
-#include <stdbool.h>
 #include <errno.h>
 #include "pmu-events/pmu-events.h"
 #include "strlist.h"
 #include <assert.h>
 #include <linux/ctype.h>
 #include <linux/zalloc.h>
+#include <subcmd/parse-options.h>
 
 struct metric_event *metricgroup__lookup(struct rblist *metric_events,
 					 struct evsel *evsel,

tools/perf/util/metricgroup.h

+// SPDX-License-Identifier: GPL-2.0-only
 #ifndef METRICGROUP_H
 #define METRICGROUP_H 1
 
-#include "linux/list.h"
-#include "rblist.h"
-#include <subcmd/parse-options.h>
-#include "evlist.h"
-#include "strbuf.h"
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <stdbool.h>
+
+struct evsel;
+struct option;
+struct rblist;
 
 struct metric_event {
 	struct rb_node nd;