[lacp] Fix debug message to match documentation

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

src/net/eth_slow.c

  * @ret name		LACP state name
  */
 static const char * eth_slow_lacp_state_name ( uint8_t state ) {
-	static char state_chars[] = "AFGSRTLX";
+	static char state_chars[] = "AFGSCDLX";
 	unsigned int i;
 
 	for ( i = 0 ; i < 8 ; i++ ) {