Fix #endif indicator comment

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index 5146605..0d16192 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -900,7 +900,7 @@
         auth_done++;
     }
     else
-#endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C || MBEDTLS_CHACHAPOLY_C */
 #if defined(MBEDTLS_CIPHER_MODE_CBC) &&                                    \
     ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) || defined(MBEDTLS_ARIA_C) )
     if( mode == MBEDTLS_MODE_CBC )