usb: gadget: lpc32xx_udc: Remove usb_endpoint_descriptor

This patch removes the utilization of struct usb_endpoint_descriptor, as done
by other drivers also. This was done on request by the USB gadget maintainers,
since this API is obsoleted.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>