Show form only on signup nodes [#1540744]

Currently the settings for the signup restrictions show up on all nodes except the user_profile.
This makes it (especially for lower-end users) a strange setting for nodes they can edit while they have nothing to do with signups.

So I would like to propose the following change in signup_restrict_by_role.module on line 12:

// old
  if($form['#node'] && $form['#node']->type.'_node_form' == $form_id && $form['#node']->type == 'user_profile') {

// new
  if($form['#node'] && $form['#node']->type.'_node_form' == $form_id && $form['#node']->signup == 1) {