Add OS variant configuration

- Debian 11 has a different TFTP path than Ubuntu 18.04

Add EFI PXE boot support with conditional

- Conditionally provide different file depending on BIOS or EFI boot
  (unsupported on BSD dhcpd implementations)

Fix galaxy metadata

Change-Id: If13d18dbf0455f8e9b27054da6f0eabbb602b71f
diff --git a/vars/Debian.yml b/vars/Debian.yml
index 01b6dc6..5e02c23 100644
--- a/vars/Debian.yml
+++ b/vars/Debian.yml
@@ -13,4 +13,4 @@
 
 tftpd_service: "tftpd-hpa"
 tftpd_groupname: "tftp"
-tftpd_boot_dir: "/var/lib/tftpboot"
+tftpd_boot_dir: "/srv/tftp"