usb: gadget: net2280: fix ep_cfg for defect7374

ep_cfg.IN_EP_ENABLE is only valid in advance mode.

Tested-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>