USB: Add nuvoton Ehci driver for w90p910 platform

Add ehci support for w90p910 platform.

Signed-off-by: Wan ZongShun <mcuos.com@gmail.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>