net: change netdev->features to u32

Quoting Ben Hutchings: we presumably won't be defining features that
can only be enabled on 64-bit architectures.

Occurences found by `grep -r` on net/, drivers/net, include/

[ Move features and vlan_features next to each other in
  struct netdev, as per Eric Dumazet's suggestion -DaveM ]

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>