docs(fwu): update firmware update design

Refactored legacy firmware design and added details about PSA
firmware updates.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I9c123b3f62580d4271dbaff0a728b6412fae7890
diff --git a/docs/resources/diagrams/Makefile b/docs/resources/diagrams/Makefile
index 4e65569..c951754 100644
--- a/docs/resources/diagrams/Makefile
+++ b/docs/resources/diagrams/Makefile
@@ -73,7 +73,13 @@
 rmm_el3_manifest_struct_layers		= "Background"
 rmm_el3_manifest_struct_opts		=
 
-all:$(RESET_PNGS) $(INT_PNGS) $(XLAT_PNG) $(RMM_PNG) $(RMM_EL3_MANIFEST_PNG)
+PSA_FWU_DIA				= PSA-FWU.dia
+PSA_FWU_PNG				= PSA-FWU.png
+
+FWU-update_struct_layers		= "background"
+FWU-update_struct_opts			=
+
+all:$(RESET_PNGS) $(INT_PNGS) $(XLAT_PNG) $(RMM_PNG) $(RMM_EL3_MANIFEST_PNG) $(PSA_FWU_PNG)
 
 $(RESET_PNGS):$(RESET_DIA)
 	$(call generate_image,$($(patsubst %.png,%_layers,$@)),$@,png,$($(patsubst %.png,%_opts,$@)),$<)
@@ -90,3 +96,6 @@
 
 $(RMM_EL3_MANIFEST_PNG):$(RMM_EL3_MANIFEST_DIA)
 	$(call generate_image,$($(patsubst %.png,%_layers,$@)),$@,png,$($(patsubst %.png,%_opts,$@)),$<)
+
+$(PSA_FWU_PNG):$(PSA_FWU_DIA)
+	$(call generate_image,$($(patsubst %.png,%_layers,$@)),$@,png,$($(patsubst %.png,%_opts,$@)),$<)