net: phy: Add SGMII Configuration for Marvell 88E1145 Initialization

Marvell phy 88E1145 configuration & initialization was missing a case
for initializing SGMII mode. This patch adds that case.

Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>