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/defaults/main.yml b/defaults/main.yml
index cd96479..85dcc6d 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -12,8 +12,9 @@
 # subnets to serve DHCP on
 dhcpd_subnets: {}
 
-# default PXE filename
+# default PXE and EFI TFTP delivered files
 dhcpd_pxe_filename: "undionly.kpxe"
+dhcpd_efi_filename: "snponly.efi"
 
 ## tftpd config
 # files to copy to the TFTP server