Check for squash in key for lmde

Fixes https://github.com/netbootxyz/netboot.xyz/issues/944

roles/netbootxyz/templates/menu/live-mint.ipxe.j2

@@ -33,7 +33,7 @@ goto flavor_select
 
 :lmde
 {% for key, value in endpoints.items() | sort %}
-{% if value.os == "mint" and value.version == "lmde" %}
+{% if value.os == "mint" and 'squash' in key and value.version == "lmde" %}
 item {{ key }} ${space} {{ value.os | title }} {{ value.version }} {{ value.flavor | title}}
 {% endif %}
 {% endfor %}