docs: cgroup-v1: convert docs to ReST and rename to *.rst

Convert the cgroup-v1 files to ReST format, in order to
allow a later addition to the admin-guide.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

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>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

Documentation/block/bfq-iosched.txt

@@ -539,7 +539,7 @@ As for cgroups-v1 (blkio controller), the exact set of stat files
 created, and kept up-to-date by bfq, depends on whether
 CONFIG_DEBUG_BLK_CGROUP is set. If it is set, then bfq creates all
 the stat files documented in
-Documentation/cgroup-v1/blkio-controller.txt. If, instead,
+Documentation/cgroup-v1/blkio-controller.rst. If, instead,
 CONFIG_DEBUG_BLK_CGROUP is not set, then bfq creates only the files
 blkio.bfq.io_service_bytes
 blkio.bfq.io_service_bytes_recursive