Use the %pM kernel extension to display the MAC address.

Also, remove the 'mac' variable and use nic->mac directly.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: NPeter Jones <pjones@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>