usb: gadget: ci13xx_udc: fix usb_ep_enable() call

commit 72c973dd

 (usb: gadget: add usb_endpoint_descriptor
to struct usb_ep) has introduced a compile error to
ci13xxx_udc. Fix it.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>