Fix IDFv5.0 include paths

Changed in commit a9fda54d39d1321005c3bc9b3cc268d0b7e9f052

components/esp_modem/examples/ap_to_pppos/main/ap_to_pppos.c

@@ -16,6 +16,10 @@
 #include "freertos/FreeRTOS.h"
 #include "freertos/event_groups.h"
 #include "network_dce.h"
+#if ESP_IDF_VERSION_MAJOR >= 5
+    #include "esp_mac.h"
+    #include "dhcpserver/dhcpserver.h"
+#endif
 
 #define EXAMPLE_ESP_WIFI_SSID      CONFIG_ESP_WIFI_SSID
 #define EXAMPLE_ESP_WIFI_PASS      CONFIG_ESP_WIFI_PASSWORD