Changing these flags requires to use dev_set_allmulti/dev_set_promiscuity
or dev_change_flags. Setting it directly causes two unwanted effects:

- the next dev_change_flags call will notice a difference between
  dev->gflags and the actual flags, enable promisc/allmulti
  mode and incorrectly update dev->gflags

- this keeps the underlying device in promisc/allmulti mode until
  the VLAN device is deleted
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>