USB: dwc3: Check for U0 before detecting missed bus-wakeup

Some of the endpoint events could be processed after U3
entry. Hence, explicitly check for U0 state before
initiating gadget wakeup on endpoint events processing.

Change-Id: I1bc295adc971f6a0e4d2409de8455511a6bb8970
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>