docs: openrisc: convert to ReST and add to documentation body

Manually convert the two openRisc documents to ReST, adding them
to the Linux documentation body.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/index.rst b/Documentation/index.rst
index 771affb..14ccbc4 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -147,6 +147,7 @@
    ia64/index
    m68k/index
    powerpc/index
+   openrisc/index
    parisc/index
    riscv/index
    s390/index