usb: dwc3: ep0: hold our lock in dwc3_gadget_ep0_set_halt

dwc3_gadget_ep0_set_halt() will be called without
locks held in some cases, so we must hold the lock
on our own. While at that, also add a version without
locks to be called in certain conditions.

Signed-off-by: Felipe Balbi <balbi@ti.com>