usb: ehci: Implement V2P mapping

Certain processor architectures, like MIPS, require that the USB
structures and transfer buffers are passed with their PA to the
USB controller. If VA is passed, the USB will not work. Add the
necessary virt_to_phys() calls into the USB EHCI code to make it
work.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>