phylib: m88e1111: enable SGMII mode

If connected via SGMII, initialize with SGMII mode configured.

Signed-off-by: Kapil Juneja <Kapil.Juneja@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>