usb: gadget: aspeed: Improve debugging when nuking

When nuking requests, it's useful to display how many were
actually nuked. It has proven handy when debugging issues
where EP0 went in a wrong state.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>