This patch pulls out the internal phy loopback setup code into a
separate function.  This cleans up the loopback test code and makes it
available for NETIF_F_LOOPBACK support later.
Signed-off-by: NMatt Carlson <mcarlson@broadcom.com>
Reviewed-by: NMichael Chan <mchan@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>