dwc3: gadget: Return -EAGAIN from dwc_gadget_func_wakeup()

usb_func_ep_queue() performs remote wakeup if func is suspended or
bus is suspended. If usb is bus suspended, resuming and remote wakeup
is performed from work context, whereas in func suspended case it
performs function remote wakeup. usb_func_ep_queue() uses different
return value based on which context remote wakeup is performed, but
it doesn't suggest if request is queued or not. With this, function
driver doesn't know status of provided request. Hence return -EAGAIN
when remote wakeup is successfully performed but provided request is
not queued with dwc_gadget_func_wakeup() API.

CRs-Fixed: 1033093
Change-Id: If8eca2047a6cc85136969295a31a55ded9a849c6
Signed-off-by: Mayank Rana <mrana@codeaurora.org>