docs: networking: convert netdev-features.txt to ReST

Not much to be done here:

- add SPDX header;
- adjust titles and chapters, adding proper markups;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/networking/checksum-offloads.rst

···
 for more details.
 
 A driver declares its offload capabilities in netdev->hw_features; see
-Documentation/networking/netdev-features.txt for more.  Note that a device
+Documentation/networking/netdev-features.rst for more.  Note that a device
 which only advertises NETIF_F_IP[V6]_CSUM must still obey the csum_start and
 csum_offset given in the SKB; if it tries to deduce these itself in hardware
 (as some NICs do) the driver should check that the values in the SKB match

Documentation/networking/index.rst

···
    mpls-sysctl
    multiqueue
    netconsole
+   netdev-features
 
 .. only::  subproject and html
 

Documentation/networking/netdev-features.txt Documentation/networking/netdev-features.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================================
 Netdev features mess and how to get out from it alive
 =====================================================
 
···
 
 
 
- Part I: Feature sets
-======================
+Part I: Feature sets
+====================
 
 Long gone are the days when a network card would just take and give packets
 verbatim.  Today's devices add multiple features and bugs (read: offloads)
···
 
 
 
- Part II: Controlling enabled features
-=======================================
+Part II: Controlling enabled features
+=====================================
 
 When current feature set (netdev->features) is to be changed, new set
 is calculated and filtered by calling ndo_fix_features callback
···
 
 
 
- Part III: Implementation hints
-================================
+Part III: Implementation hints
+==============================
 
  * ndo_fix_features:
 
···
 
 
 
- Part IV: Features
-===================
+Part IV: Features
+=================
 
 For current list of features, see include/linux/netdev_features.h.
 This section describes semantics of some of them.

include/linux/netdev_features.h

···
 	 * Add your fresh new feature above and remember to update
 	 * netdev_features_strings[] in net/core/ethtool.c and maybe
 	 * some feature mask #defines below. Please also describe it
-	 * in Documentation/networking/netdev-features.txt.
+	 * in Documentation/networking/netdev-features.rst.
 	 */
 
 	/**/NETDEV_FEATURE_COUNT