usb: host: ehci-generic: initialize PHY only when found

Call generic_phy_init() only when a PHY was found.
This will avoid a crash if no "phys" property is found in DT.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reported-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/usb/host/ehci-generic.c b/drivers/usb/host/ehci-generic.c
index 3f751f1..03f8d32 100644
--- a/drivers/usb/host/ehci-generic.c
+++ b/drivers/usb/host/ehci-generic.c
@@ -99,12 +99,13 @@
 			error("failed to get usb phy\n");
 			goto reset_err;
 		}
-	}
+	} else {
 
-	err = generic_phy_init(&priv->phy);
-	if (err) {
-		error("failed to init usb phy\n");
-		goto reset_err;
+		err = generic_phy_init(&priv->phy);
+		if (err) {
+			error("failed to init usb phy\n");
+			goto reset_err;
+		}
 	}
 
 	hccr = map_physmem(devfdt_get_addr(dev), 0x100, MAP_NOCACHE);