net/mlx4_en: Avoid changing dev->features directly in run-time

It's forbidden to manually change dev->features in run-time. Currently, this is
done in the driver to make sure that GSO_UDP_TUNNEL is advertized only when
VXLAN tunnel is set. However, since the stack actually does features intersection
with hw_enc_features, we can safely revert to advertizing features early when
registering the netdevice.

Fixes: f4a1edd5

 ('net/mlx4_en: Advertize encapsulation offloads [...]')
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>