usb: dwc3: gadget: allow running wakeup in delayed context

Adding the option of running the gadget wakeup function
from the context in which it is called, or delaying it - in case
it is called from an atomic context. This is required in order
to support a case where the gadget is in lpm and the wakeup
would result in a queue to the low-powered hardware.

Change-Id: I09fc60e75c79202c97251146aab1539de3307424
Signed-off-by: Bar Weiner <bweiner@codeaurora.org>