input: Documentation: update related file names in ff.rst

Change other related documentation file names from .txt to .rst
and be more explicit about their paths/locations.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Johann Deneux <johann.deneux@gmail.com>
Cc: Anssi Hannula <anssi.hannula@gmail.com>
Link: https://lore.kernel.org/r/20210302223523.20130-4-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Input: fix small typos in force feedback documentation

Fix small typos in the Instructions and Uploading sections. Fix a typo in
the start/stop effect example usage code.

Signed-off-by: Jean-François Têtu <jean-francois.tetu@savoirfairelinux.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

docs-rst: add input docs at main index and use kernel-figure

The input subsystem documentation got converted into ReST.

Add it to the main documentation index and use kernel-figure
for the two svg images there.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Input: use svg files instead of xfig in force feedback documentation

Now that the images got converted to svg, add them at the
ff.rst file.

NOTE: After merging upstream, the "figure" tag should be
replaced by the new "kernel-figure" tag, in order for the
SVG images to be included at the PDF files.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: create a book with Linux Input documentation

Now that all files under Documentation/input follows the ReST markup
language, rename them to *.rst and create a book for the Linux Input
subsystem.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>