net: Make UFO on master device independent of attached devices

Now that software UFO is supported, UFO can be enabled on master
devices like bridge, bond even though the attached device doesn't
support this feature in hardware.

This allows UFO to be used between KVM host and guest even when a
physical interface attached to the bridge doesn't support UFO.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>