bridge: fdb cleanup runs too often

bridge: fdb cleanup runs too often

[ Upstream commit 25442e06d20aaba7d7b16438078a562b3e4cf19b ]

It is common in end-node, non STP bridges to set forwarding
delay to zero; which causes the forwarding database cleanup
to run every clock tick. Change to run only as soon as needed
or at next ageing timer interval which ever is sooner.

Use round_jiffies_up macro rather than attempting round up
by changing value.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>