doc: Reorganise images and update links

Change-Id: I679d1499376a524bef1cfc33df995b0a719b5ac8
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/components/secure-partition-manager-design.rst b/docs/components/secure-partition-manager-design.rst
index 88052c5..ac1172c 100644
--- a/docs/components/secure-partition-manager-design.rst
+++ b/docs/components/secure-partition-manager-design.rst
@@ -814,5 +814,5 @@
 .. _SDEI Specification: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf
 .. _SMC Calling Convention: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
 
-.. |Image 1| image:: ../diagrams/secure_sw_stack_tos.png
-.. |Image 2| image:: ../diagrams/secure_sw_stack_sp.png
+.. |Image 1| image:: ../resources/diagrams/secure_sw_stack_tos.png
+.. |Image 2| image:: ../resources/diagrams/secure_sw_stack_sp.png