Move ssl_set_fallback() to work on conf

Initially thought it would be per-connection, but since max_version is in conf
too, and you need to lower that for a fallback connection, the fallback flag
should be in the same place
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index c57cb1c..a73ffe5 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -931,6 +931,9 @@
 #if defined(MBEDTLS_SSL_SESSION_TICKETS)
     unsigned int session_tickets : 1;   /*!< use session tickets?           */
 #endif
+#if defined(MBEDTLS_SSL_FALLBACK_SCSV) && defined(MBEDTLS_SSL_CLI_C)
+    unsigned int fallback : 1;      /*!< is this a fallback?                */
+#endif
 }
 mbedtls_ssl_config;
 
@@ -956,10 +959,6 @@
     unsigned badmac_seen;       /*!< records with a bad MAC received    */
 #endif
 
-#if defined(MBEDTLS_SSL_FALLBACK_SCSV) && defined(MBEDTLS_SSL_CLI_C)
-    char fallback;              /*!< flag for fallback connections    */
-#endif
-
     /*
      * Callbacks
      */
@@ -1820,10 +1819,10 @@
  *                 while, then cause failures when the server is upgraded to
  *                 support a newer TLS version.
  *
- * \param ssl      SSL context
+ * \param conf     SSL configuration
  * \param fallback MBEDTLS_SSL_IS_NOT_FALLBACK or MBEDTLS_SSL_IS_FALLBACK
  */
-void mbedtls_ssl_set_fallback( mbedtls_ssl_context *ssl, char fallback );
+void mbedtls_ssl_set_fallback( mbedtls_ssl_config *conf, char fallback );
 #endif /* MBEDTLS_SSL_FALLBACK_SCSV && MBEDTLS_SSL_CLI_C */
 
 #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)