uboot-imx

dm: usb: Add support for interrupt queues to the dm usb code

Interrupt endpoints typically are polled for a long time by the usb
controller before they return anything, so calls to submit_int_msg() can
take a long time to complete this.

To avoid this the u-boot code has the an interrupt queue mechanism / API,
add support for this to the driver-model usb code and implement it for the
dm ehci code.

See the added doc comments for more details.

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