usb: phy: Add AM335x PHY driver

This driver is a redo of my earlier attempt. It uses parts of the
generic PHY driver and uses the new control driver for the register
the phy needs to power on/off the phy. It also enables easy access for
the wakeup register which is not yet implemented.
The difference between the omap attempt is:
- no static holding variable
- one global visible function which exports a struct with callbacks to
  access the "control" registers.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/phy/Kconfig b/drivers/usb/phy/Kconfig
index f5ea339..f41c3e1 100644
--- a/drivers/usb/phy/Kconfig
+++ b/drivers/usb/phy/Kconfig
@@ -86,6 +86,18 @@
 	  This driver interacts with the "OMAP Control USB Driver" to power
 	  on/off the PHY.
 
+config AM335X_CONTROL_USB
+	tristate
+
+config AM335X_PHY_USB
+	tristate "AM335x USB PHY Driver"
+	select USB_PHY
+	select AM335X_CONTROL_USB
+	select NOP_USB_XCEIV
+	help
+	  This driver provides PHY support for that phy which part for the
+	  AM335x SoC.
+
 config SAMSUNG_USBPHY
 	tristate
 	help