Fix typo in documentation of ssl->transform_out

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 221cee3..639e3d9 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1329,7 +1329,7 @@
      * Record layer transformations
      */
     mbedtls_ssl_transform *MBEDTLS_PRIVATE(transform_in);        /*!<  current transform params (in)   */
-    mbedtls_ssl_transform *MBEDTLS_PRIVATE(transform_out);       /*!<  current transform params (in)   */
+    mbedtls_ssl_transform *MBEDTLS_PRIVATE(transform_out);       /*!<  current transform params (out)  */
     mbedtls_ssl_transform *MBEDTLS_PRIVATE(transform);           /*!<  negotiated transform params     */
     mbedtls_ssl_transform *MBEDTLS_PRIVATE(transform_negotiate); /*!<  transform params in negotiation */