Try this
if ( is_user_logged_in() && !is_admin()) {
lvkg_redirect_logged_in_user();
exit;
}
!is_admin() will make sure that this function is not called if a user is already in wp-admin or has been successfully redirected to wp-admin.
Without this check after every redirection to wp-admin, this function will be called again lvkg_redirect_logged_in_user(); hence creating an infinite loop.