This moves the SIOCSIFHWADDR code from dev_ifsioc() into a
separate new function, dev_set_mac_address().  This provides a single
entry point for all callers performing MAC address changes.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>