tls: Reset TLS maximum negotiable version

When reseting an SSL context with
mbedtls_ssl_session_reset() reset
the TLS maximum negotiable version
as configured.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 0bc18f1..0071b06 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1540,6 +1540,7 @@
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
     ssl->state = MBEDTLS_SSL_HELLO_REQUEST;
+    ssl->tls_version = ssl->conf->max_tls_version;
 
     mbedtls_ssl_session_reset_msg_layer(ssl, partial);