docs: cdrom: convert docs to ReST and rename to *.rst

The stuff there is almost already at ReST format. A
conversion for them is trivial: just add a missing titles
and fix some scape codes for them to match ReST syntax.

While here, rename the cdrom-standard.txt, with was converted
from LaTeX to ReST on the previous patch, and add it to the
index file.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index 5d1e0a4a..ac42ae4 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -7,7 +7,7 @@
    License.  See linux/COPYING for more information.
 
    Uniform CD-ROM driver for Linux.
-   See Documentation/cdrom/cdrom-standard.txt for usage information.
+   See Documentation/cdrom/cdrom-standard.rst for usage information.
 
    The routines in the file provide a uniform interface between the
    software that uses CD-ROMs and the various low-level drivers that