add socket wrapper for at framework

you can use at framework to send/recv data in socket API
example: see examples\tcp_through_module_based_at_socket
project: see board\TencentOS_tiny_EVB_MX_Plus\KEIL\tcp_through_module_based_at_socket

net/sal_module_wrapper/sal_module_wrapper.h

@@ -21,7 +21,7 @@
 #include <stdint.h>
 #include <stdio.h>
 
-typedef enum sal_proto_en {
+typedef enum sal_protocol_en {
     TOS_SAL_PROTO_TCP,
     TOS_SAL_PROTO_UDP,
 } sal_proto_t;