bridge: BH already disabled in br_fdb_cleanup()

br_fdb_cleanup() is run from timer interrupt, BH already masked.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Štefan Gula <steweg@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>