pppos-client: Refactor modem component

Merges https://github.com/espressif/esp-idf/pull/6483

examples/protocols/pppos_client/components/modem/src/sim800.c

@@ -21,6 +21,20 @@
 
 static const char *DCE_TAG = "sim800";
 
+/**
+ * @brief Macro defined for error checking
+ *
+ */
+#define DCE_CHECK(a, str, goto_tag, ...)                                              \
+    do                                                                                \
+    {                                                                                 \
+        if (!(a))                                                                     \
+        {                                                                             \
+            ESP_LOGE(DCE_TAG, "%s(%d): " str, __FUNCTION__, __LINE__, ##__VA_ARGS__); \
+            goto goto_tag;                                                            \
+        }                                                                             \
+    } while (0)
+
 /**
  * @brief Handle response from AT+CPOWD=1
  */