doc: Fix platform port inclusion

This patch:

- Adds any leftover platform ports that were not having their
  documentation built (not in the index.rst table of contents)
- Corrects a handful of RST formatting errors that cause poor
  rendering
- Reorders the list of platforms so that they are displayed
  in alphabetical order

Change-Id: If8c135a822d581c3c5c4fca2936d501ccfd2e94c
Signed-off-by: Paul Beesley <paul.beesley@arm.com>