feat(esp8266): Add WIFI socket and async APIs

1. add section to linking file

components/esp8266/include/net/if_packet.h

@@ -0,0 +1,41 @@
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _IF_PACKET_H
+#define _IF_PACKET_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * socket II type address used by low-level module whose address is base on MAC address
+ *
+ * Note: Now it just support 802.3 and 802.11 protocol, so only "sll_addr" works here
+ */
+struct sockaddr_ll {
+    unsigned short      sll_family;     // it must be AF_PACKET
+    unsigned short      sll_protocol;   // physics level protocol
+    int                 sll_ifindex;    // interface index not socket ID
+    unsigned short      sll_hatype;     // ARP hardware address type
+    unsigned char       sll_pkttype;    // packet type
+    unsigned char       sll_halen;      // hardware address length
+    unsigned char       sll_addr[8];    // address data
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _IF_PACKET_H */