usb: gadget: net2280: use udc-core's reset notifier

This patch adds support for the new udc-core reset notifier to the
net2280 driver.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>