perf namespaces: Move the conditional setns() prototype to namespaces.h

Out of util.h, to reduce its scope, and since we have a namespaces.h
header, much better to have it there, where it is related to.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-zlu81bbtccuzygh7m8nmgybc@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/namespaces.h

@@ -13,6 +13,10 @@
 #include <linux/refcount.h>
 #include <linux/types.h>
 
+#ifndef HAVE_SETNS_SUPPORT
+int setns(int fd, int nstype);
+#endif
+
 struct namespaces_event;
 
 struct namespaces {

tools/perf/util/setns.c

-#include "util.h"
+// SPDX-License-Identifier: LGPL-2.1
+
+#include "namespaces.h"
 #include <unistd.h>
 #include <sys/syscall.h>
 

tools/perf/util/util.h

@@ -67,10 +67,6 @@ char *get_current_dir_name(void);
 int sched_getcpu(void);
 #endif
 
-#ifndef HAVE_SETNS_SUPPORT
-int setns(int fd, int nstype);
-#endif
-
 extern bool perf_singlethreaded;
 
 void perf_set_singlethreaded(void);