dwc3: gadget: remove usage of wait_event_lock_irq()

dwc3_gadget_ep_dequeue() API uses wait_event_lock_irq() which takes
mutex_lock(). Hence if function driver calls this API with interrupt
and preemption disable, it results into calling sleeping function
with preemption disable. wait_event_lock_irq() API is used to wait
for stop endpoint command completion, and already existing delay
should suffice. Hence fix this issue by removing usage of
wait_event_lock_irq() from dwc3_gadget_ep_dequeue() API.

Change-Id: If31e045b37334ddeddb6e2dfb23500f356806719
Signed-off-by: Mayank Rana <mrana@codeaurora.org>