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/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 0f008ea..1d5f428 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1337,7 +1337,7 @@
 #if defined(MBEDTLS_SSL_SESSION_TICKETS) && \
     defined(MBEDTLS_SSL_SRV_C) && \
     defined(MBEDTLS_SSL_PROTO_TLS1_3)
-    uint16_t MBEDTLS_PRIVATE(new_session_tickets);   /*!< number of NewSessionTicket */
+    uint16_t MBEDTLS_PRIVATE(new_session_tickets_count);   /*!< number of NewSessionTicket */
 #endif
 
 #if defined(MBEDTLS_SSL_SRV_C)
@@ -4137,10 +4137,10 @@
     defined(MBEDTLS_SSL_SRV_C) && \
     defined(MBEDTLS_SSL_PROTO_TLS1_3)
 /**
- * \brief          Number of NewSessionTicket message that sent by server.
+ * \brief          Number of NewSessionTicket messages for the server to send
+ *                 after handshake completion.
  *                 (Default: MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS)
  *
- *
  * \param conf     SSL configuration
  * \param num_tickets   Number of NewSessionTicket.
  *