usb: gadget: net2280: fix infinite loop in irq handler

With SuperSpeed CDC NCM gadget, net2280 would get stuck in
'handle_ep_small' function. Triggering issue requires large
TCP transfer from host to USB3380.

Patch adds check for stuck condition and prevents hard lockup.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@haltian.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>