usb: gadget: aspeed: Don't reject requests on suspended devices

A disconnect may just suspend the hub in absence of a physical
disconnect detection. If we start rejecting requests, the mass
storage function gets into a spin trying to requeue the same
request for ever and hangs.

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