net/phy: add VSC8574 support

The VSC8574 is a quad-port Gigabit Ethernet transceiver with four SerDes
interfaces for quad-port dual media capability. This driver supports SGMII
and QSGMII MAC mode. For now SGMII mode is tested.

Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/include/phy.h b/include/phy.h
index 58ca273..44d5eaf 100644
--- a/include/phy.h
+++ b/include/phy.h
@@ -52,6 +52,7 @@
 	PHY_INTERFACE_MODE_MII,
 	PHY_INTERFACE_MODE_GMII,
 	PHY_INTERFACE_MODE_SGMII,
+	PHY_INTERFACE_MODE_QSGMII,
 	PHY_INTERFACE_MODE_TBI,
 	PHY_INTERFACE_MODE_RMII,
 	PHY_INTERFACE_MODE_RGMII,
@@ -67,6 +68,7 @@
 	[PHY_INTERFACE_MODE_MII]		= "mii",
 	[PHY_INTERFACE_MODE_GMII]		= "gmii",
 	[PHY_INTERFACE_MODE_SGMII]		= "sgmii",
+	[PHY_INTERFACE_MODE_QSGMII]		= "qsgmii",
 	[PHY_INTERFACE_MODE_TBI]		= "tbi",
 	[PHY_INTERFACE_MODE_RMII]		= "rmii",
 	[PHY_INTERFACE_MODE_RGMII]		= "rgmii",