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

The kbuild documentation clearly shows that the documents
there are written at different times: some use markdown,
some use their own peculiar logic to split sections.

Convert everything to ReST without affecting too much
the author's style and avoiding adding uneeded markups.

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>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

drivers/net/wireless/intel/iwlegacy/Kconfig

@@ -32,7 +32,7 @@ config IWL4965
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwl4965.
 
 config IWL3945
@@ -58,7 +58,7 @@ config IWL3945
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwl3945.
 
 menu "iwl3945 / iwl4965 Debugging Options"

drivers/net/wireless/intel/iwlwifi/Kconfig

@@ -40,7 +40,7 @@ config IWLWIFI
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwlwifi.
 
 if IWLWIFI