usb: dwc2: gadget: On USB RESET reset device address to zero

Reseted DEVADDR field in DCFG to zero on USB RESET.

Device address in DCFG register does not reset to zero,
which required to pass enumeration, after disconnect and
reconnect.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>