i40e/i40evf: Reset VLAN filter count when resetting

When we do a reset, all the VLAN filters get added again. Therefore we also
want to reset the VLAN count to 0 or we quickly run out of filters.

Change-ID: I459f26851e22204dc8b8999928ad87cde8170119
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>