usb: otg: utils: add facilities in phy lib to support multiple PHYs of same type

In order to add support for multipe PHY's of the same type, new API's
for adding PHY and getting PHY has been added. Now the binding
information for the PHY and controller should be done in platform file
using usb_bind_phy API. And for getting a PHY, the device pointer of the
USB controller and an index should be passed. Based on the binding
information that is added in the platform file, usb_get_phy_dev will return the
appropriate PHY.
Already existing API's to add and get phy by type is not removed. These
API's are deprecated and will be removed once all the platforms start to
use the new API.

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