Altera TSE: Add support for no PHY

This patch avoids PHY and MDIO probing if no PHY chip is present.
This is the case mainly in optical links where there is no need for
PHY chip, and therefore no need of MDIO. In this scenario Ethernet
MAC is directly connected to an optical module through an external
SFP transceiver.

Signed-off-by: Walter Lozano <walter@vanguardiasur.com.ar>
Signed-off-by: David S. Miller <davem@davemloft.net>