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>
diff --git a/drivers/phy/phy-sun4i-usb.c b/drivers/phy/phy-sun4i-usb.c
index e2eb688d..623c714 100644
--- a/drivers/phy/phy-sun4i-usb.c
+++ b/drivers/phy/phy-sun4i-usb.c
@@ -373,7 +373,7 @@
 	sun4i_usb_phy_write(phy, PHY_SQUELCH_DETECT, enabled ? 0 : 2, 2);
 }
 
-static struct phy_ops sun4i_usb_phy_ops = {
+static const struct phy_ops sun4i_usb_phy_ops = {
 	.init		= sun4i_usb_phy_init,
 	.exit		= sun4i_usb_phy_exit,
 	.power_on	= sun4i_usb_phy_power_on,