usb: phy: add Keystone usb phy driver

Add Keystone platform USB PHY driver support. Current main purpose
of this driver is to enable the PHY reference clock gate on the
Keystone SoC. Otherwise it is a nop PHY.

[ balbi@ti.com : add COMPILE_TEST as a possible dependency
	make sure drvdata is initialized before adding PHY ]

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: WingMan Kwok <w-kwok2@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/phy/Kconfig b/drivers/usb/phy/Kconfig
index 4f22762..54bebba3 100644
--- a/drivers/usb/phy/Kconfig
+++ b/drivers/usb/phy/Kconfig
@@ -48,6 +48,15 @@
 	  This driver can also be built as a module.  If so, the module
 	  will be called isp1301_omap.
 
+config KEYSTONE_USB_PHY
+	tristate "Keystone USB PHY Driver"
+	depends on ARCH_KEYSTONE || COMPILE_TEST
+	select NOP_USB_XCEIV
+	help
+	  Enable this to support Keystone USB phy. This driver provides
+	  interface to interact with USB 2.0 and USB 3.0 PHY that is part
+	  of the Keystone SOC.
+
 config MV_U3D_PHY
 	bool "Marvell USB 3.0 PHY controller Driver"
 	depends on CPU_MMP3