bridge: leave carrier on for empty bridge

bridge: leave carrier on for empty bridge

[ Upstream commit b64b73d7d0c480f75684519c6134e79d50c1b341 ]

This resolves a regression seen by some users of bridging.
Some users use the bridge like a dummy device.
They expect to be able to put an IPv6 address on the device
with no ports attached. Although there are better ways of doing
this, there is no reason to not allow it.

Note: the bridge still will reflect the state of ports in the
bridge if there are any added.

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>