Since commit beeb74 we already check in modussl_mbedtls whether this
function is provided by the ESP-IDF before calling it, thus we no longer
need to define it here in order to compile.
Removing it so that if CONFIG_MBEDTLS_DEBUG is defined we do not cause any
'multiple definition' compile errors.
Signed-off-by: Daniël van de Giessen <daniel@dvdgiessen.nl>