usb: Add support for VIA VT8500 and compatibles in EHCI HCD

VIA and WonderMedia Systems-on-Chip feature a standard EHCI host
controller. This adds necessary glue to use the standard driver
with these systems.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>