fix(applications/drv_ec800k):修复获取信号强度csq时栈溢出问题

applications/drv_ec800k.c

@@ -174,7 +174,7 @@ int16_t BSP_LTE_GetCGATT(int16_t retry) {
 
 #define CSQ_CMD_RESP "+CSQ:"
 int BSP_LTE_GetCSQ(void) {
-  int8_t ret = -1;
+  int ret = -1;
   char *pstr = NULL;
 
   if (0 == BSP_LTE_SendCmd(AT_CSQ, DEFAULT_EXPECT, DEFAULT_ERROR,