net/e1000: update network information when macaddr is changed in guest

net/e1000: update network information when macaddr is changed in guest

If we change macaddr in guest by 'ifconfig eth0 hw ether 12:12:12:34:35:36',
the mac register of e1000 is already updated, but we don't update
network information in qemu. Therefor, the information in monitor
is wrong.

This patch updates nic info when the second part of macaddr is written.

Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>