cxgb4: offload VLAN flows regardless of VLAN ethtype

VLAN flows never get offloaded unless ivlan_vld is set in filter spec.
It's not compulsory for vlan_ethtype to be set.

So, always enable ivlan_vld bit for offloading VLAN flows regardless of
vlan_ethtype is set or not.

Fixes: ad9af3e0 (cxgb4: add tc flower match support for vlan)
Signed-off-by: Raju Rangoju <rajur@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>