net, phy, cpsw: fix NULL pointer deference

if phy_connect() did not find a phy, phydev is NULL and
following code in cpsw_phy_init() crashes. Fix this.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Cc: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Tom Rini <trini@ti.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
diff --git a/drivers/net/cpsw.c b/drivers/net/cpsw.c
index 9bab71a..39240d9 100644
--- a/drivers/net/cpsw.c
+++ b/drivers/net/cpsw.c
@@ -568,9 +568,14 @@
 static void cpsw_slave_update_link(struct cpsw_slave *slave,
 				   struct cpsw_priv *priv, int *link)
 {
-	struct phy_device *phy = priv->phydev;
+	struct phy_device *phy;
 	u32 mac_control = 0;
 
+	phy = priv->phydev;
+
+	if (!phy)
+		return;
+
 	phy_startup(phy);
 	*link = phy->link;
 
@@ -947,6 +952,9 @@
 			dev,
 			slave->data->phy_if);
 
+	if (!phydev)
+		return -1;
+
 	phydev->supported &= supported;
 	phydev->advertising = phydev->supported;