Write key_share base on key_exchange mode.

In ServerHello, write key share should base on key_exchange mode, not
base on configuration.

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 6013079..15656fe 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1803,7 +1803,7 @@
     }
     p += output_len;
 
-    if( mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
+    if( mbedtls_ssl_tls13_key_exchange_mode_with_ephemeral( ssl ) )
     {
         if( is_hrr )
             ret = ssl_tls13_write_hrr_key_share_ext( ssl, p, end, &output_len );