Define specific mode for ChachaPoly

The TLS layer is checking for mode, such as GCM, CCM, CBC, STREAM. ChachaPoly
needs to have its own mode, even if it's used just one cipher, in order to
allow consistent handling of mode in the TLS layer.

include/mbedtls/cipher.h

@@ -186,6 +186,7 @@ typedef enum {
     MBEDTLS_MODE_STREAM,                 /**< The stream cipher mode. */
     MBEDTLS_MODE_CCM,                    /**< The CCM cipher mode. */
     MBEDTLS_MODE_XTS,                    /**< The XTS cipher mode. */
+    MBEDTLS_MODE_CHACHAPOLY,             /**< The ChaCha-Poly cipher mode. */
 } mbedtls_cipher_mode_t;
 
 /** Supported cipher padding types. */

library/cipher_wrap.c

@@ -2040,7 +2040,7 @@ static const mbedtls_cipher_base_t chachapoly_base_info = {
 };
 static const mbedtls_cipher_info_t chachapoly_info = {
     MBEDTLS_CIPHER_CHACHA20_POLY1305,
-    MBEDTLS_MODE_NONE,
+    MBEDTLS_MODE_CHACHAPOLY,
     256,
     "CHACHA20-POLY1305",
     12,