fix(mbedtls): Build issue in dynamic buffer feature

Fix build issue in mbedTLS dynamic buffer feature with
`CONFIG_MBEDTLS_DHM_C` enabled case. Also added a build
configuration for the test coverage.

Closes https://github.com/espressif/esp-idf/issues/11770

components/mbedtls/port/dynamic/esp_mbedtls_dynamic_impl.c

@@ -474,8 +474,8 @@ void esp_mbedtls_free_dhm(mbedtls_ssl_context *ssl)
 {
 #ifdef CONFIG_MBEDTLS_DHM_C
     const mbedtls_ssl_config *conf = mbedtls_ssl_context_get_config(ssl);
-    mbedtls_mpi_free((mbedtls_mpi *)conf->MBEDTLS_PRIVATE(dhm_P));
-    mbedtls_mpi_free((mbedtls_mpi *)conf->MBEDTLS_PRIVATE(dhm_G));
+    mbedtls_mpi_free((mbedtls_mpi *)&conf->MBEDTLS_PRIVATE(dhm_P));
+    mbedtls_mpi_free((mbedtls_mpi *)&conf->MBEDTLS_PRIVATE(dhm_G));
 #endif /* CONFIG_MBEDTLS_DHM_C */
 }
 

examples/protocols/esp_http_client/sdkconfig.ci.ssldyn

@@ -11,4 +11,5 @@ CONFIG_ESP_HTTP_CLIENT_ENABLE_BASIC_AUTH=y
 CONFIG_MBEDTLS_DYNAMIC_BUFFER=y
 CONFIG_MBEDTLS_DYNAMIC_FREE_PEER_CERT=y
 CONFIG_MBEDTLS_DYNAMIC_FREE_CONFIG_DATA=y
+CONFIG_MBEDTLS_DHM_C=y
 CONFIG_EXAMPLE_HTTP_ENDPOINT="httpbin.espressif.cn"