refactor(changelog): change all occurrences of RSS to RSE

Changes all occurrences of "RSS" and "rss" in the code and build files
to "RSE" and "rse".

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: I66a6c87c158b14e18cba25ea6c6e0809e30008ca
diff --git a/changelog.yaml b/changelog.yaml
index b7f281c..f38dd85 100644
--- a/changelog.yaml
+++ b/changelog.yaml
@@ -955,11 +955,12 @@
             deprecated:
               - drivers/arm/mhu
 
-          - title: RSS
-            scope: rss
+          - title: RSE
+            scope: rse
 
             deprecated:
               - drivers/arm/rss
+              - rss
 
           - title: TZC
             scope: tzc