doc: Reorganise images and update links

Change-Id: I679d1499376a524bef1cfc33df995b0a719b5ac8
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/design/firmware-design.rst b/docs/design/firmware-design.rst
index e9384e6..710d26d 100644
--- a/docs/design/firmware-design.rst
+++ b/docs/design/firmware-design.rst
@@ -2679,4 +2679,4 @@
 .. _ROMLIB Design: romlib-design.rst
 .. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT) Armv8-A (ARM DEN0006D): https://developer.arm.com/docs/den0006/latest/trusted-board-boot-requirements-client-tbbr-client-armv8-a
 
-.. |Image 1| image:: diagrams/rt-svc-descs-layout.png?raw=true
+.. |Image 1| image:: ../resources/diagrams/rt-svc-descs-layout.png