musb: Add device-model support to the musb-host u-boot glue

Add device-model support to the musb-host u-boot glue, note this only
adds device-model support to the musb-core glue code, it does not add
support for device-model to any of the SoC specific musb glue code.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Simon Glass <sjg@chromium.org>