phy: Constify struct phy_ops variables

The phy_ops variables are never modified after initialized in these
drivers, so make them const.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/phy-armada375-usb2.c

@@ -51,7 +51,7 @@ static int armada375_usb_phy_init(struct phy *phy)
 	return 0;
 }
 
-static struct phy_ops armada375_usb_phy_ops = {
+static const struct phy_ops armada375_usb_phy_ops = {
 	.init = armada375_usb_phy_init,
 	.owner = THIS_MODULE,
 };