i40e: Setting i40e_down bit for tx_timeout

If tx_timeout recovery failed, then it becomes necessary to set
i40e_down bit before actually shutdown the connection.

Change-ID: Iaac81df0e302116571827aa0cff450697fbb7fa3
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>