Platform: RSE: Rename RSE platform files

Renames all 'rss' files to 'rse'. Avoids changes unrelated to moving
files in this commit to keep to commit history clearer.

Signed-off-by: Jamie Fox <jamie.fox@arm.com>
Change-Id: I321aa2cdff6117c869a7128d2866207efd9b3309
diff --git a/docs/platform/platform_introduction.rst b/docs/platform/platform_introduction.rst
index 3301415..0075e73 100644
--- a/docs/platform/platform_introduction.rst
+++ b/docs/platform/platform_introduction.rst
@@ -64,7 +64,7 @@
 
     - Runtime Security Engine (RSE):
 
-        - :doc:`RSE. </platform/arm/rss/readme>`
+        - :doc:`RSE. </platform/arm/rse/readme>`
 
 The document :doc:`Platform Deprecation and Removal </integration_guide/platform/platform_deprecation>`
 lists the deprecated platforms, removed from the upstream.