net: netdev-features.txt update to Documentation/networking/00-INDEX

Update netdev-features.txt entry in 00-INDEX to incorporate
feedback by Michał Mirosław.

v2: restored tabs that were inadvertently changed to spaces in v1.
sorry for the error.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>