rtnetlink: Do not generate notifications for CHANGEADDR event

Changing hardware address generates redundant messages:

[LINK]11: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether 02:02:02:02:02:02 brd ff:ff:ff:ff:ff:ff

[LINK]11: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether 02:02:02:02:02:02 brd ff:ff:ff:ff:ff:ff

Do not send a notification for the CHANGEADDR notifier.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>