net: bridge: don't print in br_switchdev_set_port_flag

For the netlink interface, propagate errors through extack rather than
simply printing them to the console. For the sysfs interface, we still
print to the console, but at least that's one layer higher than in
switchdev, which also allows us to silently ignore the offloading of
flags if that is ever needed in the future.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>