usb: dwc3: Disable ep cmd completion events before clearing R/S

Stopping the endpoints (end transfer command) before halting the
controller can generate asynchronous events and can prevent halting
the controller (due to pending events that needs to be acked). As
driver is not taking any action in end transfer command completion,
issue end transfer command without setting IOC(interrupt on complete)
bit to prevent any events generated from command completion. For GSI
endpoints ack the pending events which are posted during end transfer
command and block ringing of GSI doorbell after halting the controller.

Change-Id: I538c12ca91ff095ac6d26a597fd0ed779327a91a
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>