net: qcom/emac: always use autonegotiation to configure the SGMII link

Regardless of how the external PHY is configured, the internal PHY
(the "SGMII" block) is capable of configuring the SGMII link automatically.
When the external PHY link comes up, regardless of how it is configured,
the SGMII link is configured automatically.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>