dt-bindings: usb: Convert USB HCD generic binding to YAML

The USB HCD generic binding is used by many USB host bindings.

In order to allow the DT validation to happen on those, let's create a YAML
description for that generic binding that can be referenced later on.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>