phy: add a NO-OP phy driver

This driver is used to stub PHY operations in a driver (USB, SATA).
This is useful when the 'client' driver (USB, SATA, ...) uses the PHY
framework and there is no actual PHY harwdare to drive.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>

drivers/phy/nop-phy.c

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2017 Texas Instruments Incorporated - http://www.ti.com/
+ * Written by Jean-Jacques Hiblot  <jjhiblot@ti.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/device.h>
+#include <generic-phy.h>
+
+static const struct udevice_id nop_phy_ids[] = {
+	{ .compatible = "nop-phy" },
+	{ }
+};
+
+static struct phy_ops nop_phy_ops = {
+};
+
+U_BOOT_DRIVER(nop_phy) = {
+	.name	= "nop_phy",
+	.id	= UCLASS_PHY,
+	.of_match = nop_phy_ids,
+	.ops = &nop_phy_ops,
+};