usb: phy: mxs: Add auto clock and power setting

The auto setting is used to open related power and clocks
automatically after receiving wakeup signal.

With this feature, the PHY's clock and power can be recovered
correctly from low power mode, it is guaranteed by IC logic.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>