Revert "change max_early_data_size source"

This reverts commit 3d8d6a770f3a0f3045820970bc4a5d6ee7df8e10.

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 84129f7..df10cc6 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -3232,10 +3232,10 @@
 
     MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_EARLY_DATA, p, 0);
     MBEDTLS_PUT_UINT16_BE(4, p, 2);
-    MBEDTLS_PUT_UINT32_BE(ssl->session->max_early_data_size, p, 4);
+    MBEDTLS_PUT_UINT32_BE(ssl->conf->max_early_data_size, p, 4);
     MBEDTLS_SSL_DEBUG_MSG(
         4, ("Sent max_early_data_size=%u",
-            (unsigned int) ssl->session->max_early_data_size));
+            (unsigned int) ssl->conf->max_early_data_size));
 
     *out_len = 8;