[eap] Ignore any received EAP responses

EAP responses (including our own) may be broadcast by switches but are
not of interest to us and can be safely ignored if received.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/eap.h

@@ -26,6 +26,9 @@ struct eap_header {
 /** EAP request */
 #define EAP_CODE_REQUEST 1
 
+/** EAP response */
+#define EAP_CODE_RESPONSE 2
+
 /** EAP request */
 struct eap_request {
 	/** Header */