[fix] 修复使用lwip 2.1.2作为协议栈，并使能dhcp server选项时，编译报错问题。

components/net/lwip_dhcpd/dhcp_server.c

@@ -80,6 +80,22 @@
 #define LWIP_DHCP   1
 #include <lwip/dhcp.h>
 
+#ifndef DHCP_CLIENT_PORT
+#define DHCP_CLIENT_PORT  68
+#endif
+
+#ifndef DHCP_SERVER_PORT
+#define DHCP_SERVER_PORT  67
+#endif
+
+#ifndef ETHADDR32_COPY
+#define ETHADDR32_COPY(dst, src)  SMEMCPY(dst, src, ETH_HWADDR_LEN)
+#endif
+
+#ifndef ETHADDR16_COPY
+#define ETHADDR16_COPY(dst, src)  SMEMCPY(dst, src, ETH_HWADDR_LEN)
+#endif
+
 /* buffer size for receive DHCP packet */
 #define BUFSZ               1024