usb: dwc_otg: support to the latest usb gadget driver.

usb: dwc_otg: support to the latest usb gadget driver.

For gadget driver, usb_ep_caps is a new structrue in usb_ep, and its
attribute will be check in usb_ep_autoconfig method, so we need to do
some initialization work at ep creating.

Meanwhile, the process of android gadget driver have been changed,
correspondingly, udc_start and udc_stop are invoked differently from
before, so dwc_otg_gadget_stop method need to refactor and ajust
the new process.

Change-Id: Id1e20d4c265e0d382b0f36f6e729681f9c94c947
Signed-off-by: Frank Wang <frank.wang@rock-chips.com>