fix various issues

- Improve comments
- Align count variable name to `new_session_tickets_count`
- move tickets_count init to handshake init

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 065b354..de6bae2 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -674,6 +674,7 @@
     !defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
     mbedtls_pk_init( &handshake->peer_pubkey );
 #endif
+
 }
 
 void mbedtls_ssl_transform_init( mbedtls_ssl_transform *transform )
@@ -763,6 +764,13 @@
     mbedtls_ssl_transform_init( ssl->transform_negotiate );
     ssl_handshake_params_init( ssl->handshake );
 
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3) && \
+    defined(MBEDTLS_SSL_SRV_C) && \
+    defined(MBEDTLS_SSL_SESSION_TICKETS)
+    ssl->handshake->new_session_tickets_count =
+        ssl->conf->new_session_tickets_count ;
+#endif
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
     {
@@ -2612,11 +2620,11 @@
 
 #if defined(MBEDTLS_SSL_SRV_C)
 
-#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3) && defined(MBEDTLS_SSL_SESSION_TICKETS)
 void mbedtls_ssl_conf_new_session_tickets( mbedtls_ssl_config *conf,
                                            uint16_t num_tickets )
 {
-    conf->new_session_tickets = num_tickets;
+    conf->new_session_tickets_count = num_tickets;
 }
 #endif
 
@@ -4653,7 +4661,7 @@
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
-#if defined(MBEDTLS_SSL_SRV_C)
+#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_SESSION_TICKETS)
     mbedtls_ssl_conf_new_session_tickets(
         conf, MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS );
 #endif