bridge: Avoid 'statement with no effect' compiler warnings

Instead of issuing (0) statements when !CONFIG_SYSFS which will cause
'warning: ', we'll use inline statements instead. This will effectively
do the same thing, but suppress any unnecessary warnings.

Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>