Update links to TF-A documentation

Update the links to the TF-A documentation to point to
trustedfirmware.org rather than Github.

Change-Id: Ib49b90b6733cdf6acd17d95e6d4968ac162bd150
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/docs/design.rst b/docs/design.rst
index 5a13d79..91815d0 100644
--- a/docs/design.rst
+++ b/docs/design.rst
@@ -245,7 +245,7 @@
 
 --------------
 
-*Copyright (c) 2018, Arm Limited. All rights reserved.*
+*Copyright (c) 2018-2019, Arm Limited. All rights reserved.*
 
 .. _Summary of build options: user-guide.rst#summary-of-build-options
-.. _Firmware Update: https://github.com/ARM-software/arm-trusted-firmware/blob/master/docs/firmware-update.rst
+.. _Firmware Update: https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/about/docs/firmware-update.rst