arm: omap: usb: create common enums and structures for ehci and ohci

Create the ehci and ohci specific platform data structures.
The port enum values are made common for both ehci and ohci.

Signed-off-by: Keshava Munegowda <keshava_mgowda@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>