drivers: usb: Make usb device-tree fixup code architecture independent

move usb device tree fixup code from "arch/powerpc/" to "drivers/usb/"
so that it works independent of architecture it is running on

Signed-off-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Signed-off-by: Nikhil Badola <nikhil.badola@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>