fix various issues

- typo error
- replace `ssl->hanshake` with handshake

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index a39949c..f854998 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -547,7 +547,7 @@
         }
 
         MBEDTLS_SSL_PRINT_EXTS( 3, MBEDTLS_SSL_HS_CERTIFICATE,
-                                ssl->handshake->received_extensions );
+                                handshake->received_extensions );
     }
 
 exit: