[doc] moved otbn/README.md file for new layout
`mv hw/ip/otbn/{doc/_index,README}.md` will be performed
for the new doc layout,
because the former is a better overview of the module.
This file is moved on it's own commit so no files are modified,
and thus git can track the file moves.
Signed-off-by: Hugo McNally <hugo.mcnally@gmail.com>
diff --git a/hw/ip/otbn/README.md b/hw/ip/otbn/doc/developer-guide.md
similarity index 100%
rename from hw/ip/otbn/README.md
rename to hw/ip/otbn/doc/developer-guide.md