perf tools: Suggest using -f to override perf.data file ownership message

# id
  uid=0(root) gid=0(root) groups=0(root)
  # ls -la perf.data
  -rw-------. 1 acme acme 20720 Jul  8 11:35 perf.data

Previously:

  # perf report
  file perf.data not owned by current user or root

Now:

  # perf report
  File perf.data not owned by current user or root (use -f to override)

Suggested-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-0j2wuuegnhv3gljbil8ld6kx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/data.c

@@ -65,7 +65,7 @@ static int open_file_read(struct perf_data_file *file)
 		goto out_close;
 
 	if (!file->force && st.st_uid && (st.st_uid != geteuid())) {
-		pr_err("file %s not owned by current user or root\n",
+		pr_err("File %s not owned by current user or root (use -f to override)\n",
 		       file->path);
 		goto out_close;
 	}