ixgbe: Fix a memory leak in IEEE DCB

The driver was freeing memory in shutdown instead of remove.  As a result
we were leaking memory if IEEE DCB was enabled and we loaded/unloaded the
driver.  This change moves the freeing of the memory into the remove
routine where it belongs.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>