Switch to proper filename of bootloader list

roles/netbootxyz/tasks/generate_checksums.yml

@@ -27,7 +27,7 @@
 
 - name: Reset bootloader filename to first in list
   ansible.builtin.set_fact:
-    bootloader_filename: "{{ bootloader_file | first }}"
+    bootloader_filename: "{{ bootloader_disks | first }}"
 
 - name: Generate netboot.xyz index template
   ansible.builtin.template: