net: bridge: use switchdev for port flags set through sysfs too

Looking through patchwork I don't see that there was any consensus to
use switchdev notifiers only in case of netlink provided port flags but
not sysfs (as a sort of deprecation, punishment or anything like that),
so we should probably keep the user interface consistent in terms of
functionality.

http://patchwork.ozlabs.org/project/netdev/patch/20170605092043.3523-3-jiri@resnulli.us/
http://patchwork.ozlabs.org/project/netdev/patch/20170608064428.4785-3-jiri@resnulli.us/



Fixes: 3922285d ("net: bridge: Add support for offloading port attributes")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>