fix various issues

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 8c5a32d..1b5861c 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1532,7 +1532,7 @@
                                                size_t total_hs_len );
 
 /*
- * Update checksum of handshake message
+ * Update checksum of handshake messages.
  */
 void mbedtls_ssl_tls13_add_hs_msg_to_checksum( mbedtls_ssl_context *ssl,
                                                unsigned hs_type,