usb: dwc3: Allow controller to enter LPM in bus suspend

usb: dwc3: Allow controller to enter LPM in bus suspend

Add a DT property that decides whether to allow controller
low power mode upon bus suspend, which will be invoked by
the OTG state machine.

It is also required to take the core out of LPM in case
ep_queue is called by the upper layers. In this case,
remote wakeup sequence will be initiated once the core
is out of LPM.

[jackp@codeaurora.org: Squashed with dwc3 changes from
 "usb: dwc3: Add new OTG state OTG_STATE_B_SUSPENDED"]
Signed-off-by: Jack Pham <jackp@codeaurora.org>