Modifying the flags of an IP addr object needs to be protected against
eg. concurrent removal of the same object from the IP table.

Fixes: 5f78e29c ("qeth: optimize IP handling in rx_mode callback")
Signed-off-by: NJulian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>