AT模块在执行AT+CLOSE并返回OK后，在实际关闭前（上报URC前）仍然有
可能接收到数据。所以接收数据时需要判断状态是否为AT_SOCKET_CONNECT。

另，at_recv_notice_cb在拒绝数据包时，没有释放数据包内存，从而导致
内在泄漏。

失败现象为“找不到EAGAIN”，此问题由libc改动引发。

Revert "fix the bug that rx_notice out of sync when data received after last rt_device_read() is zero"

2、sal socket在支持多网卡时，sal_getaddrinfo从A网卡获取的地址信息，在sal_freeaddrinfo释放时必须由A网卡进行释放

fix at_client, avoid creating the same client repeatedly and prevent working exceptions and memory leaks.

lenght -> length
sfotware -> software

Signed-off-by: RGW <rgw5267@gmail.com>

Signed-off-by: chenyong <1521761801@qq.com>

Signed-off-by: chenyong <1521761801@qq.com>

len值如果不给初始值0，到最后__exit的时候，result = len会导致result的值变成一个不可预估的值，进而导致mbedtls库的while循环无法正常结束，其中mebedtls中发生异常的地方在ssl_tls.c文件中的mbedtls_ssl_flush_output函数while( ssl->out_left > 0 )，因为out_left 是一个无符号整型，退出的条件只能是 out_left = 0,又因为这里面的len没有给初始值0，返回出来的值是一个很大的整型数字，导致了mbedtls中的死循环

Signed-off-by: chenyong <1521761801@qq.com>

Signed-off-by: chenyong <1521761801@qq.com>

- AT Socket feature supports multi-client connections;
- Fix `send data error, current socket (0) state (0) is error` issue when the socket is closed;
- Improve dirty data processing when AT device hard reset;
- Improve `at_obj_set_urc_table()` fucntion, Support for setting multiple URC tables;
- Improve RAW data print format;