bridge: remove oflags from setlink/dellink.

Commit 02dba438

 ("bridge: fix setlink/dellink notifications") removed usage of oflags in
both rtnl_bridge_setlink() and rtnl_bridge_dellink() methods. This patch removes this variable as it is no
longer needed.

Signed-off-by: Rami Rosen <rami.rosen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>