ixgbe: fix driver behaviour after issuing VFLR

Since VFLR doesn't clear VFMBMEM (VF Mailbox Memory)
and is not re-enabling queues correctly we should fix
this behavior.

Signed-off-by: Sebastian Basierski <sebastianx.basierski@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>