iavf: fix inverted Rx hash condition leading to disabled hash

Condition, which checks whether the netdev has hashing enabled is
inverted. Basically, the tagged commit effectively disabled passing flow
hash from descriptor to skb, unless user *disables* it via Ethtool.
Commit a876c3ba ("i40e/i40evf: properly report Rx packet hash")
fixed this problem, but only for i40e.
Invert the condition now in iavf and unblock passing hash to skbs again.

Fixes: 857942fd ("i40e: Fix Rx hash reported to the stack by our driver")
Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>