net: switchdev: don't abort unsupported operations

There is no need to abort attribute setting or object addition, if the
prepare phase returned operation not supported.

Thus, abort these two transactions only if the error is not -EOPNOTSUPP.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Scott Feldman <sfeldma@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>