usb: dwc2: gadget: use reset detect interrupt

ResetDet interrupt is used to detect a reset of the bus
while the controller is suspended.
This may happens for example when using Command Verifier.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>