netdev-linux: Report netdev change events when mac changed.

netdev-linux: Report netdev change events when mac changed.

When mac addr of ports on bridge has been changed, for example,

$ ip link set dev eth0 address 00:11:22:33:44:55

we should reconfigure the datapath id and mac addr of local port.
But now openvswitch dont do that as expected.

A simple example of how to reproduce it:

$ ovs-vsctl add-br br0
$ ifconfig br0 			# for example, mac is c6:c6:d7:46:b4:4b
$ ip link set dev br0 address 00:11:22:33:44:55
$ ifconfig br0 			# mac of br0 will be 00:11:22:33:44:55

then repeat:
$ ip link set dev br0 address 00:11:22:33:44:55
$ ifconfig br0 			# mac of br0 will be c6:c6:d7:46:b4:4b

This patch reports the mac changed event when ports changed, then
openvswitch will reconfigure the datapath id and mac addr of local
port.

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>