usb: otg: add an api to bind the usb controller and phy

usb: otg: add an api to bind the usb controller and phy

In order to support platforms which has multiple PHY's (of same type) and
which has multiple USB controllers, a new design is adopted wherin the binding
information (between the PHY and the USB controller) should be passed to the
PHY library from platform specific file (board file).
So added a new API to pass the binding information.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>