ipvlan: set hw_enc_features like macvlan

Allow encapsulated packets sent to tunnels layered over ipvlan to use
offloads rather than forcing SW fallbacks.

Since commit f21e5077

 ("macvlan: add offload features for
encapsulation"), macvlan has set dev->hw_enc_features to include
everything in dev->features; do likewise in ipvlan.

Signed-off-by: Bill Sommerfeld <wsommerfeld@google.com>
Acked-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>