docs: networking: convert fore200e.txt to ReST

- add SPDX header;
- adjust title markup;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/fore200e.txt → Documentation/networking/fore200e.rst

+.. SPDX-License-Identifier: GPL-2.0
 
+=============================================
 FORE Systems PCA-200E/SBA-200E ATM NIC driver
----------------------------------------------
+=============================================
 
 This driver adds support for the FORE Systems 200E-series ATM adapters
 to the Linux operating system. It is based on the earlier PCA-200E driver

Documentation/networking/index.rst

@@ -57,6 +57,7 @@ Contents:
    eql
    fib_trie
    filter
+   fore200e
 
 .. only::  subproject and html
 

drivers/atm/Kconfig

@@ -336,7 +336,7 @@ config ATM_FORE200E
 	  on PCI and SBUS hosts. Say Y (or M to compile as a module
 	  named fore_200e) here if you have one of these ATM adapters.
 
-	  See the file <file:Documentation/networking/fore200e.txt> for
+	  See the file <file:Documentation/networking/fore200e.rst> for
 	  further details.
 
 config ATM_FORE200E_USE_TASKLET