Added instructions on how to create the DH parameters files.

hostapd/hostapd.conf

@@ -468,6 +468,8 @@ eap_server=0
 # ephemeral DH keys. This can be used to achieve forward secrecy. If the file
 # is in DSA parameters format, it will be automatically converted into DH
 # params. This parameter is required if anonymous EAP-FAST is used.
+# You can generate DH parameters file with OpenSSL, e.g.,
+# "openssl dhparam -out /etc/hostapd.dh.pem 1024"
 #dh_file=/etc/hostapd.dh.pem
 
 # Configuration data for EAP-SIM database/authentication gateway interface.