phy: mvebu-cp110-comphy: fix mux error check

The mux value is retrieved from the mvebu_comphy_get_mux() function
which returns an int. In mvebu_comphy_power_on() this int is stored to a
u32 and a check is made to ensure it's not negative. Which is wrong.
This fixes it.

Fixes: d0438bd6aa09 ("phy: add the mvebu cp110 comphy driver")
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/marvell/phy-mvebu-cp110-comphy.c

@@ -468,8 +468,8 @@ static int mvebu_comphy_power_on(struct phy *phy)
 {
 	struct mvebu_comphy_lane *lane = phy_get_drvdata(phy);
 	struct mvebu_comphy_priv *priv = lane->priv;
-	int ret;
-	u32 mux, val;
+	int ret, mux;
+	u32 val;
 
 	mux = mvebu_comphy_get_mux(lane->id, lane->port, lane->mode);
 	if (mux < 0)