SPEAr: Add interface information in initialization

Few Designware peripheral registers need to be modified based on the
ethernet interface selected by the board. This patch supports interface
information in ethernet driver

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/net/designware.h b/drivers/net/designware.h
index abf729d..40020bf 100644
--- a/drivers/net/designware.h
+++ b/drivers/net/designware.h
@@ -234,6 +234,7 @@
 
 struct dw_eth_dev {
 	u32 address;
+	u32 interface;
 	u32 speed;
 	u32 duplex;
 	u32 tx_currdescnum;