Fix formatting issues in Renesas board markdown

Fix formatting issues in Renesas board markdown

Changes:
- python-markdown is particular about indentation being 4 spaces
  for lists, fix various indentation so that the generated page
  has properly numbered lists and indentation levels.
- Replace some remaining XML markup that was breaking the page
  rendering with code blocks.  This fixes the U-Boot output examples.
- Simplify the indentation in section 11 by using section headers
  for the multimedia and ICCOM information instead of a list.
  This avoids a lot of extra indentation in the markdown and wastes
  less horizontal space on the generated page.
- Add a couple more elinux.org links where it seemed appropriate.
- Tweak wording in a couple of spots to read better.

Bug-AGL: SPEC-3708

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I6b643804b11ee7dae11a7a5569abe57337270f86
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/25956
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>