rijndael.c: Do not include functions already present for ESP-IDF ESP-IDF platform already has rijndaelEncrypt() defined causing link errors. This change excludes rijndaelEncrypt() and rijndaelKeySetupEnc() functions if building for the ESP-IDF platform. Change-Id: I54595784e74848a47a2546d88a1c74506015fa58 Signed-off-by: Jon Shallow <supjps-libcoap@jpshallow.com> Signed-off-by: Olaf Bergmann <bergmann@tzi.org>