[NET]: Use newer is_multicast_ether_addr() in some files

This uses is_multicast_ether_addr() because it has recently been
changed to do the same thing these seperate tests are doing.

Signed-off-by: Kris Katterjohn <kjak@users.sourceforge.net>
Signed-off-by: David S. Miller <davem@davemloft.net>