do_pin_fd() will already print out an error message if something
goes wrong.  Printing another error is unnecessary and will break
JSON output, since error messages are full objects:
$ bpftool -jp prog load tracex1_kern.o /sys/fs/bpf/a
{
    "error": "can't pin the object (/sys/fs/bpf/a): File exists"
},{
    "error": "failed to pin program"
}
Fixes: 49a086c201a9 ("bpftool: implement prog load command")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
                return -1;
        }
 
-       if (do_pin_fd(prog_fd, argv[1])) {
-               p_err("failed to pin program");
+       if (do_pin_fd(prog_fd, argv[1]))
                return -1;
-       }
 
        if (json_output)
                jsonw_null(json_wtr);