docs: driver-model: convert docs to ReST and rename to *.rst

Convert the various documents at the driver-model, preparing
them to be part of the driver-api book.

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: Jeff Kirsher <jeffrey.t.kirsher@intel.com> # ice
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpio/gpio-cs5535.c

@@ -41,7 +41,7 @@ MODULE_PARM_DESC(mask, "GPIO channel mask.");
 
 /*
  * FIXME: convert this singleton driver to use the state container
- * design pattern, see Documentation/driver-model/design-patterns.txt
+ * design pattern, see Documentation/driver-model/design-patterns.rst
  */
 static struct cs5535_gpio_chip {
 	struct gpio_chip chip;