Docs: Platform documentation rules

- Minimal rules for a platform documentation
- Adjust existing platforms according to the rules

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: Idcb85f8ed5d55aa6406cd48cdfcb558d92ff0647
diff --git a/docs/index.rst b/docs/index.rst
index 4d2f3fe..6f4571d 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -85,7 +85,7 @@
     :maxdepth: 1
     :hidden:
 
-    Platform Selection<platform/index>
+    Platforms <platform/index>
     building/tfm_build_instruction
     configuration/index
     integration_guide/index