fastd: add method = salsa2012+gmac for site legacy

fastd/fastd.conf

@@ -12,6 +12,9 @@ method "aes128-ctr+umac";
 #method "aes128-ctr+umac";	# Not supported by CPU on this machine
 {%- endif %}
 method "salsa2012+umac";
+{%- if site == 'legacy' %}
+method "salsa2012+gmac";
+{%- endif %}
 
 
 {#- nodes{4,6} VPNs #}