usb: dwc3: Process event buffer when pullup is disabled

Commit c8ba6a8b ("usb: dwc3: Disable ep0 and interrupts when
clearing run/stop") added functionality to ignore processing of
event buffer if pullup is not enabled. In some cases, it is
observed that pullup is disabled but controller has raised few
endpoint complete events. dwc3_msm_suspend() API aborts USB LPM
sequence if USB event buffer is not empty which would results
into no APPS power collpase. Fix this issue by processing event
buffer when pullup is disabled which clears event buffer.

Change-Id: I45e9ea15c6a2351b8af970f0afef66df609595f6
Signed-off-by: Mayank Rana <mrana@codeaurora.org>