i40evf: fix memory leak on unused interfaces

If the driver is loaded and then unloaded before the interface is
brought up, then it will allocate a MAC filter entry and never free it.
To fix this, on unload, run through the mac filter list and free all the
entries. We also do this during reset recovery when the driver cannot
contact the PF and needs to shut down completely.

Change-ID: I15fabd67eb4a1bfc57605a7db60d0b5d819839db
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>